7. A sink is filled with 54 quarts of water. The function q = f(t) = 54 - 2.5t gives the volume of water in a sink, i quarts, t seconds after removing the stopper. a. Find f-1. b. What does the input of f-1 represent? What does the output of f-1 represent? c. How long will it take for the sink to drain completely? d. How long will it take for the sink to lose one-third of its water?