Rachael's backyard swimming pool is being emptied by a pump. the amount of water in the pool (w, measured in gallons) at any time (t, measured in hours) is given by the following equation: w = -250t + 9000a. how many gallons of water are being pumped out each hour? explain. b. after 11 hours, how much water is left in the pool? explain. c. how much water was in the pool at the start? explain. d. how long will it take the pool to empty? explain.