## Homework Statement

Here is a picture of the problem: http://i3.photobucket.com/albums/y62/Phio/23.jpg" [Broken]

A = xy = 780

cost = 8x+2y

## The Attempt at a Solution

c = 8x + (1560/x)

c'= 8 - ( 1560/(x^2) )

0 = 8 - ( 1560/(x^2) )

x^2 = 195

x= $$\sqrt{195}$$

x = 13.96 = 14

I don't know what to do from here...I still can't figure out what the answer is. I think it must be either B or D.

Last edited by a moderator:

rock.freak667
Homework Helper

Find the corresponding value of y.

oh now I see it...it's obvious. The answer is B.

Thanks!