A star initially has $10^{44}$ deuterons. It produces energy via the processes $\,^2_1\mathrm{H} + \,^2_1\mathrm{H} \to \,^3_1\mathrm{H} + \,^1_1\mathrm{H}$ and $\,^2_1\mathrm{H} + \,^3_1\mathrm{H} \to \,^4_2\mathrm{He} + \,^1_0\mathrm{n}$. The masses of the nuclei are: $m(\,^2\mathrm{H}) = 2.014\,\text{amu}$, $m(\,^1\mathrm{H}) = 1.007\,\text{amu}$, $m(\,^3\mathrm{H}) = 1.008\,\text{amu}$, $m(\,^4\mathrm{He}) = 4.001\,\text{amu}$. If the average power radiated by the star is $10^{20}\,\text{W}$, the deuteron supply of the star is exhausted in a time of the order of