An electric hot plate is maintaned at a temperature of 350 and is used to keep the solution just boiling at 95. The solution is cointaned in an enamelled cast -iron vessel of wall thickeness 25mm and enamel thickness 0.8mm. The heat transfer coefficient for the boiling solution is 5.5kw/m^2k, and the thermal conductivities of cast iron and enamel are 50 and 1.05w/mk respectively. Calculate the resistance to the heat transfer for unit area, and the rate of heat transfer per unit area.