(c)Stefan's law.From Stefan-Boltzman's law, the energy of the thermal radiation emitted per unit time by a blackbody of surface area A is given by, u=σAT4 Where σ  is Stefan's constant.Suppose a body at temperature T is kept in a room at temperature T0​. According to Stefan's law, energy of the thermal radiation emitted by the body per unit time is u=eσAT4 Here, e is the emissivity of the body.The energy absorbed per unit time by the body is (due to the radiation emitted by the walls of the room Δu=eσAT04​. Thus, the net loss of thermal energy per unit time is Δu=eσA(T4−T04​) ...(i) Newton law of cooling is given by(dT)/(dt)=−bA(T−T0​) This can be obtained from equation (i) by considering the temperature difference to be small and doing the binomial expansion.