Answer:
C(x,y,z)=6*x*y+10*x*z+10*y*z
Step-by-step explanation:
Lets assume that x is width, y is length and z is height. To find the area of the top and bottom surfaces we need to simply multiply length and width.
x*y
There is a 2 surface exist (top and bottom) we need to multiply this value with 2 again.
2*x*y
and the cost is 3$ for per square foot and the cost for top and bottom is:
6*x*y$
Surface areas of side surfaces are multiply of width, height and length, height:
x*z+y*z
There are 4 side surfaces exist. Therefore the are need to be multiply with 2.
2*x*z+2*y*z
and the cost is 5$ for per square foot and the cost for side surfaces is:
10*x*z+10*y*z
Total equality for cost is C(x,y,z)=6*x*y+10*x*z+10*y*z
