The relevant formula is the Stefan-Boltzmann formula
$\begin{align*}\frac{\Delta Q}{\Delta t} = \sigma A T^4\end{align*}$
Here $\Delta Q$ / $\Delta t$ is the rate at which energy is radiated from the blackbody, $\sigma$ is the Stefan-Boltzmann constant, $A$ is the area of the blackbody, and $T$ is the temperature of the blackbody in $^{\circ} \mbox{ K}$ . So, doubling $T$ while holding everything else constant increases the power radiated by the blackbody by a factor of $16$ . Thus, answer (E) is correct.

Solution to 1986 Problem 46