24. An old urn is discovered that looks like a cylinder except that the side is wavy. The urn is 6 inches high. Scientists want to estimate the volume of the urn so they measure its circumference at intervals of 2 inches, and produce the following data, measuring to the nearest tenth of an inch.
a. Use a left-hand Riemann sum to estimate the volume of the cylinder.
b. Someone suggests that the scientists model the volume as being obtained by rotating the curve
y = 20 about the y-axis. Set up, but do not evaluate, an integral expression that gives that volume.