The volume formula is area of base×height. In this case, we are working with rectangles, so the formula is l×w×h. We have to find the volume of each block and add them together. Top rectangle: 12×30×4=1440. Middle rectangle: 30×36×4=4320. Bottom rectangle: 30×60×4=7200. 7200+4320+1440=12960 inches squared.
