Water is to be heated from 10°c to 80°c as it flows through a 2-cm-internal-diameter, 7-m-long tube. the tube is equipped with an electric resistance heater, which provides uniform heating throughout the surface of the tube. the outer surface of the heater is well insulated, so that in steady op- eration all the heat generated in the heater is transferred to the water in the tube. if the system is to provide hot water at a rate of 8 l/min, determine the power rating of the resistance heater. also, estimate the inner surface temperature of the pipe at the exit.