Monopolist optimizing price: Marginal revenue

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Monopolist optimizing price: Marginal revenue발음듣기

Now that we figured out the total revenue given any quantity, and we've also been able to express it algebraically, I want to think about what the marginal revenue is at any one of these points.발음듣기

To think about marginal revenue, marginal revenue is just how much does our total revenue change, given some change in our quantity.발음듣기

Then later, we can use that so that we can optimize the profit for our monopoly over here.발음듣기

I'm going to try to do it without calculus.발음듣기

It actually would be very straightforward to do it with calculus because we're essentially just trying to find the slope at any point along this curve, but I'll try to do it algebraically and maybe it will even give you a little intuition for what we end up doing eventually in calculus.발음듣기

The first thing I want to do is essentially find the slope, the slope right over here.발음듣기

The best way to find the slope right over here is say how much does my total revenue change if I have a very small change in quantity?발음듣기

If I have a very small change in quantity, how much does my total revenue change?발음듣기

Let me think about it this way.발음듣기

The other ones I will be able to approximate a little bit easier.발음듣기

Let's think of it this way.발음듣기

If my quantity is 0, my total revenue is 0.발음듣기

That one's easy.발음듣기

If I increase my quantity very, very, very, very little, so let's just make it 0.001, what is going to be my total revenue?발음듣기

We could think about it in terms of this curve right over here, or we could just use this expression, which we derived from price times quantity, and we will get, I'll get my calculator out, if our quantity is .001, our total revenue is going to be negative ...발음듣기

Let me turn the calculator on.발음듣기

Total revenue is going to be -.001², squared, so that's that part, plus 6 times .001, 6 times .001.발음듣기

That's going to be our total revenue.발음듣기

It's going to be 0.005999.발음듣기

It's 0.00599.발음듣기

Now we can figure out or get a pretty good approximation for that marginal revenue right at that point.발음듣기

Our change in quantity is .001, so our ΔQ, this right over here is 0.001.발음듣기

That's our change in quantity, and our change in revenue is 0.00599, and so we just have to divide.발음듣기

We just have to divide .005999, that top one, our change in total revenue divided by our change in quantity, divided by .001.발음듣기

We get 5.99999.발음듣기

If you try it with even smaller numbers, if you tried this with .00000001, you'll get 5-point, and you'll get even more 9s going on.발음듣기

The closer that you get, the smaller your change in, and this is what you essentially do in calculus.발음듣기

You try to find a super small change right over here.발음듣기

This is essentially going to be 6.발음듣기

Our marginal revenue at this point is essentially going to be 6.발음듣기

What I want to do is I'm going to plot marginal revenue here on our demand curve as well or on this axis where we've already plotted our demand curve.발음듣기

When our quantity is 0, our marginal revenue, if we just barely increase quantity, the incremental total revenue we get is going to be 6.발음듣기

I'll just plot it.발음듣기

I'll just plot it right over there.발음듣기

That makes sense.발음듣기

The marginal benefit in the market is 6, right at that point.발음듣기

If we were to just sell a drop of orange juice or I guess we're selling oranges in this case, not juice, but if we were to sell a millionth of a pound of oranges, we would get the equivalent of roughly $6 per pound for that millionth of a pound because that's the marginal benefit for that very first incremental chunk of orange out there in the market, so it makes complete sense.발음듣기

Now let's think about the slope at these other points.발음듣기

These, I'm going to approximate.발음듣기

I could do it this way, but I'll just approximate it.발음듣기

I'll just approximate it by using other points.발음듣기

If I want to find the slope right over here, when our quantity is equal to 1, the slope would look like, the slope would look like that.발음듣기

I'm going to approximate it by finding the slope between these two points.발음듣기

I am going to approximate it, and actually, it's going to be a very good approximation.발음듣기

I'll do it later with calculus to show that it is a very good approximation.발음듣기

But I'm going to approximate it by the slope between these two points.발음듣기

Between those two points, our change in quantity is 2, and our change in total revenue is 8.발음듣기

Our change in total revenue is 8.발음듣기

When we produced 2, or 2,000 pounds, our total revenue was $8,000.발음듣기

So we have a change in total revenue of 8, or 8,000, I guess we could say, divided by a change in quantity of 2,000, so our marginal revenue at this point is 8 divided by 2, or 8,000 divided by 2,000, which is $4 per pound.발음듣기

When our quantity is 1, our marginal revenue is $4 per pound.발음듣기

It is $4 per pound, just like that.발음듣기

Now, let's think about the marginal revenue when our quantity is 2.발음듣기

To do that, I'm going to find the slope between these two points.발음듣기

We really want to find the slope of that line, but it looks like the slope between these two points is a pretty good approximation.발음듣기

It's actually almost an exact number because of the way that this is just a parabola, so we can actually do this.발음듣기

But anyway, this is fairly straightforward.발음듣기

Once again, our change in quantity is 2, and our change in total revenue, our change in total revenue is, we're going from 5 to 9, which is 4.발음듣기

This was 9 right over here from the last video.발음듣기

Or you could say it's $4,000 divided by 2,000 pounds gives you $2 per pound.발음듣기

Our marginal revenue right over here, if we have quantity of 2, is $2 per pound.발음듣기

Right at that point, for that incremental millionth of an ounce that we're going to sell them oranges, we're getting the equivalent of $2 a pound of increased total revenue from doing that.발음듣기

Let's just do one more point here, and I think you'll see why I'm only going to do one more point.발음듣기

If we try to go up here, and we try to figure out what is the marginal revenue or if we essentially say what is the slope there, how much do we get an increase in revenue if we just barely increase our quantity, and this is actually easier to look at.발음듣기

This is a maximum point right over here, in the calculus terms.발음듣기

The slope up there is 0.발음듣기

We can even see that by approximating the slope between the slope between these two points.발음듣기

We have some change in quantity, but we have no change in total revenue, so right at that point.발음듣기

Right over here, the slope is barely positive.발음듣기

Right at that point, the slope is 0, and then right past it, it becomes barely negative.발음듣기

But right at that point, our marginal revenue is 0.발음듣기

When our quantity is 3,000 pounds, our marginal revenue is 0.발음듣기

Then after that, our marginal revenue gets negative.발음듣기

Over here, our marginal revenue gets more and more negative.발음듣기

But something very interesting happens.발음듣기

When we plot our marginal revenue curve, or our line, in this case, we are getting a line, we are getting a line, we are getting a line that is twice as steep, twice as steep as our demand curve.발음듣기

This is actually generalizable.발음듣기

If we have a linear demand curve like this, it can be defined as a line, then your marginal revenue curve for the monopolist will also be a linear downward-sloping curve or downward-sloping line, and it will have twice the slope.발음듣기

This slope over here was -1.발음듣기

This slope over here is -2.발음듣기

For every increase in quantity, the price goes down by 2; increase in quantity, price goes down by 2; increase in quantity, price goes down by 2.발음듣기

This is marginal revenue.발음듣기

Let's remind our self, we've been doing all of this algebra and all of this math here, what is marginal revenue telling us?발음듣기

This was the demand curve.발음듣기

It tells us for any given price what quantity is demanded or for any given quantity, what is the incremental marginal benefit, or I guess what's the price at which they could sell that quantity.발음듣기

From that, we were able to figure out the total revenue as a function of quantity, and from that total revenue, we were able to say, well, look, if at any of these quantities, if we were to increase a little bit more, if we were to increase quantity a little bit more, how much is our revenue increasing?발음듣기

Obviously, we want to keep increasing quantity while our revenue is ... while the marginal revenue we get is larger than our marginal cost.발음듣기

I'll take that up in the next video.발음듣기

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