Volume of the box =
V = x (60 - 2x)(20 - 2x)
= x( 1200 - 40x - 120x + 4x^2)
= 4x^3 - 160x^2 + 1200x
Finding the derivative of V:-
dV/dx = 12x^2 - 320x + 1200 = 0 for a maximum volume
this gives x = 4.51 , 22.15 (22.15 cannot be value of x because it would make 20 - 2x negative.
So for a maximum volume x = 4.51
and Maximum volume = (4.51)(60-9.02)(20-9.02) = 2524.5 cm^3 Answer