A rectangular tank with a base 4 feet by 5 feet and a height of 4 feet is full of water (see figure). The water weighs 62.4 pounds per cubic foot. How much work is done in pumping water out over the top edge in order to empty the following amounts? 4 ft 4 fi 3 ft (a) half of the tank ft - lb (b) all of the tank ft - lb