The temperature in an electric oven is 160 °C. The temperature at the outer surface in the kitchen is 50 °C. The oven (surface area = 1.6 m2) is insulated with material that has a thickness of 0.020 m and a thermal conductivity of . (a) How much energy is used to operate the oven for six hours? (b) At a price of $0.10 per kilowatt · hour for electrical energy, what is the cost of operating the oven?