$A$ star initially has $10^{40}$ deuterons. It produces energy via the processes:
$_1H^2 + _1H^2 \to _1H^3 + p$
$_1H^2 + _1H^3 \to _2He^4 + n$
The masses of the nuclei are as follows:
$M(H^2) = 2.014 \, amu; \, M(p) = 1.007 \, amu;$
$M(n) = 1.008 \, amu; \, M(He^4) = 4.001 \, amu$
If the average power radiated by the star is $10^{16} \, W$, the deuteron supply of the star is exhausted in a time of the order of:

• A
  $10^6 \, sec$
• B
  $10^8 \, sec$
• C
  $10^{12} \, sec$
• D
  $10^{16} \, sec$