00:01
Okay, so the problem gives us a marginal cost function.
00:06
Here, i've called the marginal cost function c prime of x, because for all the economics formulas, you can really think of the word marginal as saying derivative.
00:15
So in this case, it's the derivative of the cost function that i'm calling c of x, and then an initial cost, so a cost for zero units of $100 ,000.
00:27
Here, we are first asked to find the cost of extracting the first 50 -tenths, of ore from the mine, and then we're asked for the cost for the next 50 tons.
00:36
So in both the cases, we're going to use the net change theorem, which i've indicated on the right side kind of up in the corner.
00:43
So for the first 50 tons, it's pretty straightforward.
00:46
We just need the value c of 50, which will be the cost of extracting 50 tons.
00:54
And so going by what the formula says, we have that as c of zero plus the integral from 0 to 50, and now this marginal cost function was given in thousands of dollars per ton.
01:09
So what i'm going to do is multiply the whole thing by 1 ,000 to make it come out as dollars.
01:15
So it matches what co0 is.
01:17
So for that, we will get 600 plus 8x dx.
01:27
So this is going to be 100 ,000 plus 600x.
01:35
Evaluated from 0 and 50 plus 8 over 2 x squared evaluated at 0 and 50.
01:45
Now these two zeros cancel because when you plug in 0 for the x in either of those terms, it's just going to equal 0.
01:56
So we don't have to evaluate those...