A spherical ball A of surface area 20  is kept at the cantre of a hollow spherical shell B of area . The surface of A & the inner surface of B emit as blackbodies. assume that the thermal conductivity of B IS POOR &  that of A is high & there is vacuum between A&B. the heat capacities of A & B are 42J per *C & 82J per*C. Initially the temp of A is 100*C & that of B is 20*C. find the rate of change of temp of A &  that of B @ this instant.