I'm worried about the process of solving this problem, can anyone help me? We are to make a rectangular box, including the top, that has a volume of 144 cubic inches and for which the base is twice as wide as it is deep. The bottom, which must be strong, is made of a material that is three times as expensive as that used for the sides and the top. Find the dimensions of the box that minimize its cost. I know I must have two equations with two variables in total but I'm not sure what to do after that. Maybe 144=(2x)(x)(y)? and another Thanks to anyone who can shed some light on this for me, I've been trying for a bit but not sure where to start.