Two boxes are shown below. The length and height of box 2 are double the length and height of box 1, and the widths are the same. The volume of box 1 is 324 cubic inches.

Real gross domestic product: a) will increase if the price level increases. b) can change from one year to the next even if there is no change in output. c) will increase if the level of output increases. d) is a measure of inflation.