How long an electric lamp of $100 w$ be kept glowing by fusion of $2.0\;kg$ of deuterium ?

Question

$\begin{array}{1 1} 0.499 \times 10^4 \;years \\ 4.99 \times 10^4 \;years \\ 49.9 \times 10^4 \;years \\ 49.9 \times 10^3 \;years \end{array}$