A small sphere (2.5 cm in diameter) is placed in a heating oven. The oven cavity is a 30 cm cube filled with air at 101 kPa (abs); it contains 3% water vapor at 810 K, and its walls are at 1370 K. The emissivity of the sphere is equal to 0.44 – 0.00018 T, where T is the surface temperature in K. When the surface temperature of the sphere is 810 K, determine
(a) The total irradiation received by the walls of the oven from the sphere 

(b) The net heat transfer by radiation between the sphere and the walls of the oven

(c) The radiant heat transfer coefficient