the volume is very simple, is simply the product of the 3 dimensions, the length*width*height, so namely is 4*2*3.
now, how much material? well, that'd be the surface area, check the picture below. So the container is really just 6 rectangles stacked up to each other at the edges.
left and right, two 2x3 rectangles.
top and bottom, two 4x2 rectangles.
front and back, two 4x3 rectangles.
get the area of each, sum them up, and that's the surface area of the rectangular prism, and therefore that's how much material was used.
