A rectangular box with no top and two parallel partitions se

A rectangular box with no top and two parallel partitions (see the figure) is to be made to hold a volume of 8 cubic inches. Find the dimensions that will require the least amount of material.

here we need to get x/2 , so that it covers the cube frm above. and z should be made twise on the other side when we close rectangular box to make cube

we need y and x/2 and 2z for 8 cube inche.( asume y=8,x=16,z=4).