00:01
All right.
00:02
So number 61, we have a definition for average cost.
00:06
And this makes sense because average cost is the cost per unit.
00:11
Right? so you take all that cost and you divided up per unit.
00:15
So if you have, you know, 17 units and divided by 17, you're going to get the average cost.
00:18
So it's a definition.
00:19
It's a good one.
00:21
So then the question part a is specifically asking you to find a prime in terms of c prime and c, which sounds horrible when you first read it.
00:29
But what they're actually asking for you to do is to do, to use the product rule.
00:33
So hopefully you remember that off the top of your head.
00:35
If not, go back and look it up and see if you can find it.
00:38
And when you do that, you can really look at c of x divided by x as c of x times x to the negative one power.
00:47
I mean, you can use the quotient rule too, but it's the same thing.
00:52
So when you do that, you can go ahead and apply the product rule and you get this long looking thing right here, right? and that's got c prime over here and it's got the derivative of this part so then we're left with this part right here and we can bring it all under one denominator by multiplying this fraction by one which is x over x right which is the same as one so when we do that we're down here to this point right here things are looking pretty good honestly and at this point we can go ahead and just rewrite it as what the book has now there's one thing that the book has that you're going to have to ignore if you look right here, this says x prime.
01:32
I don't even know why that's there.
01:33
If there were an x prime, it would be the derivative of x, which is always one...