A star initially has $\;10^{40}\;$ deutrons . If produces energy via the process $\;_{1}H^{1}+_{1}H^{2} \to _{1}H^{3}+P\;$ and $\;_{1}H^{2}+_{1}H^{3} \to _{2}He^{4}\;.$ If the average power radiated by star is $\;10^{16}W\;,$ the deutron supply of star is exhausted in a time of order of \[\] (The masses of nuclei are $\;m(H^2)=2.014\;amu\;,m(p)=1.007 amu , \; m(n)=1.0084 amu ,\; m(H)=4.001 amu))$