A 2-shell passes and 4-tube passes heat exchanger is used to heat glycerin from 20\degc to 50\degc by hot water, which enters the thin-walled 2-cm-diameter tubes at 80\degc and leaves at 40\degc . The total length of the tubes in the heat exchanger is 60 m. The convection heat transfer coefficient is 25 W/m2.K on the glycerin (shell) side and 160 W/m2.K on the water (tube) side. Determine the rate of heat transfer in the heat exchanger (a) before any fouling and (b) after fouling with a fouling factor of 0.0006 m2.K/W occurs on the outer surfaces of the tubes.