Cubic Functions Question

[Aqualim]

Having trouble with this question, can anybody help me out?

[dekoyl]

a) You know that the sum of all edges' length = 60cm as it's made from 60 cm of wire.
 So: 8x + 4y = 60
 Then you can let y = ...

b) Volume = length x width x height = . Since you know what y = ... from part (a), you can do it in terms of .

c) V = what you found in part (b). Differentiate this and find the local maximum point. The x-coordinate of the maximum point will be side length (x) that yields greatest volume.