In the manufacture of nitric acid, ammonia and preheated air are mixed to form a gas containing 10 mole% NH3 at 600oC. (The ammonia is not preheated, since if it were, it will decompose to N2 and H2). The mixture is then catalytically oxidized to form NO2, which is absorbed in water to form HNO3. If ammonia enters the gas blending (mixing) unit at 25oC at a rate of 520 kg/h, and heat is lost from the mixer to its surroundings at a rate of 7 kW, determine the temperature to which the air must be preheated. (Use the first two terms of the Cp equation for air).