According to the Stefan-Boltzmann law, the rate at which a black body emits radiant energy is directly proportional to the fourth power of its absolute temperature ($E \propto T^4$). Given the temperature of the black body, $T_C = 727^\circ\text{C}$. Converting this to absolute temperature (Kelvin scale): $T = T_C + 273 = 727 + 273 = 1000 \text{ K}$. Therefore, the rate at which it emits energy is proportional to $T^4 = (1000)^4$.