00:01
So this question has a lot of parts to it.
00:03
Let's just go through it step by step.
00:05
So we start off knowing the total cost and the marginal cost and the demand, and we know there's nine firms.
00:13
So from this, we can ascertain the fixed cost, the variable cost, and the average total cost.
00:19
How do we do that? well, first, if we just stop and look at our total cost equation here, we see there's a component, 50, that has nothing to do with the quantity.
00:29
That's going to be our fixed cost.
00:31
And sure enough, fixed cost equals 50.
00:33
There's a second component here that is dependent upon the quantity, and therefore, that's going to be our variable cost.
00:43
Our formula for average total cost is really simple.
00:46
It's just the total cost divided by q.
00:49
So that's going to be 50 plus 1 1ā2 squared all over q.
00:57
And we can simplify that to this.
01:06
50 over q plus q over 2.
01:13
Okay? so that's just the average total cost just written a different way.
01:18
All right.
01:18
For the next part, if you actually go from quantity of 5 through quantity of 15 and you plug those numbers for q into the average total cost and the marginal cost equations, you're going to get two lines that looks on.
01:32
Something like this.
01:34
Okay? so the average total cost cuts through the marginal cost at the minimum of the average total cost, right? that's part of the definition of those two lines.
01:45
So we can already tell that in the long run, the equilibrium is going to be here.
01:52
Okay? in the long run, equilibrium is going to have a price of 10 and each firm is going to produce 10 units.
01:59
Okay.
02:01
So what is the actual firm supply curve? well, it turns out that because marginal cost, right, just equals q, and we always produce when marginal revenue equals marginal cost, turns out that the supply of each firm is just going to be equal to the price, because marginal revenue is equal to the price.
02:26
All right.
02:27
So for parts d and e, we know that p is going to be q over nine because there's nine firms.
02:35
And if we just plug these numbers into our demand equation, we can therefore find that the equilibrium price for part e is going to be 12, and the equilibrium quantity is going to be 108.
02:48
And again, this is just using the demand equation that we were given, which is qd equals 120 minus p...