A shipping crate has a square base with side length x feet and no top. The crate must have a volume of 500 ft3. The wood for the base costs \10persquarefoot,andthewoodforthefoursidescosts4 per square foot. Which of the following expressions gives the total material cost C, in dollars, as a function of x after the volume condition has been used to eliminate the height?
a) C(x)=10x2+x8000
b) C(x)=10x2+x2000
c) C(x)=14x2+x8000
d) C(x)=10x2+x28000