A double-pipe heat exchanger is intended to be designed to cool 6 cubic feet of hot oil per minute from 210 F to 90 F. The cooling process will use cooling water entering the heat exchanger at 70 F and flowing at 12 cubic ft/min. The heat exchanger is made of BWG 16 copper pipe with a diameter of 0.5 inches; It consists of 11 ft sections. Calculate how many parts the heat exchanger consists of if it operates a) parallel and b) counter current. (U:105btu/h.square.F cp,pet:055 btu/lb.F cp,water: 1.0 btu/lb.F density oil:52lb/cubic ft density water:62.4 lb/cubic ft)