7. Set up, but do not simplify or evaluate, the integrals to find the volumes of the solids obtained by rotating the region bounded by the curves y = x and y = x about the following lines. Use whichever method your prefer; clearly specify which method you use for each solid. (a) (10 pts.) The x-axis. (b) (10 pts.) The y-axis. (c) (10 pts.) y = 2