The mass of a regulation tennis ball is $57 \mathrm{~g}$ (although it can vary slightly), and tests have shown that the ball is in contact with the tennis racket for $30 \mathrm{~ms}$. (This number can also vary, depending on the racket and swing.) We shall assume a $30.0 \mathrm{~ms}$ contact time. One of the fastest-known served tennis balls was served by "Big Bill" Tilden in 1931 , and its speed was measured to be $73 \mathrm{~m} / \mathrm{s}$. (a) What impulse and what total force did Big Bill exert on the tennis ball in his record serve?
(b) If Big Bill's opponent returned his serve with a speed of $55 \mathrm{~m} / \mathrm{s}$, what total force and what impulse did he exert on the ball, assuming only horizontal motion?