3. A hydrocarbon stream is to be cooled from 200F to 130F using 10,800lb/h of water with a range of 75F to 125F. A double pipe heat exchanger comprised of 25ft long carbon steel hairpins will be used. The inner and outer pipes are 1.5- and 3.5 -in. schedule 40 , respectively. The hydrocarbon will flow through the inner pipe and the heat-transfer coefficient for this stream has been determined: hi=200Btu/hft2F. Fouling factors of 0.001hft2F/Btu for water and 0.002 hft2F/Btu for the hydrocarbon are specified. How many hairpins will be required