A 12in.by24in. sheet of cardboard is folded in half to form a 12in.by12in. rectangle as shown in the accompanying gure. Then four congruent squares of side length x are cut from the comers of the folded redangle. The sheet is unfolded, and the six tabs are folded up to form a box with sides and a lid. Complete parts (a) through (f) below. xx T l l ______. x XXI |- 24in. "l |- 12m+| |- 24in. "l a. 'Write a formula V[)