(a) From Stefan’s law
$E = \sigma T^{4}A$
Given, $T = 727℃ = (727 + 273) = 1000$ K
$\ \ \ \ \ \ \ \ \ A = 5 \times 10^{- 4}\ m^{2}$
$\therefore\ \ \ \ Energy = \left( 5.67 \times 10^{- 8} \right)(1000)^{4}\left( 5 \times 10^{- 4} \right)60$
$\therefore\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ E = 1.7 \times 10^{3}$ J