6.a) Find the net rate at which heat is exchanged by radiation between a polished stainless steel tube (1.59cm in dia., 50cm long, emissivity =0.25) and the surrounding surfaces at 300K if the surface temperature of the tube is (i) 350K; (ii) 400K; and (iii) 450K. b) Calculate the shape factor F1-2 for the configurations given in Fig. c) The variation of the monochromatic irradiation (in W/m2m ) falling on a surface is as follows: H=400sin(8)for08mH=0for8m Calculate the reflectivity of the surface if =0.24for03m=0.10for3m