Hi

I need help on the following question:

1) A symmetrical gutter is made of metal sheeting 30cm. wide by bending it twice as shown in the cross section. Find an expression for the area of the cross section and hence find the value of for the gutter to have maximum carrying capacity.

http://img94.imageshack.us/img94/2024/diagramit.jpg

This is what i have try to do so far.

I know that Area of a square is L*W and Area of 2 triangles is

so

Make

Don't think this is correct.

P.S