Air at 18°C (c_p = 1006 J/kg·K) is to be heated to 58°C by hot oil at 80°C (c_p = 2150 J/kg·K) in a cross-flow heat exchanger with air mixed and oil unmixed. The product of heat transfer surface area and the overall heat transfer coefficient is 750 W/K and the mass flow rate of air is twice that of oil. Determine

(a) The effectiveness of the heat exchanger,

(b) The mass flow rate of air,

(c) The rate of heat transfer.