(1a). Black body has emissivity value of 1, but in reality, the emissivity of real objects is less than 1. Why?? (1.5 marks) (1b). The tungsten sphere of 220 mm radius is at a temperature of 29C. If the power radiated by sphere is 97 W, calculate its emissivity value? (2marks) (1c).If the same sphere is enclosed in room whose walls are kept at -25C, what is the net flow rate of energy out of the sphere in Watts (W) (1.5 marks)