A first order reaction is $50\%$ completed in $1.26 \times 10^{14}\;s$ . how much time would it take for $100 \%$ completion ?

Question

$\begin{array}{1 1} 1.26 \times 10^{15}\;S \\ 2.52 \times 10^{14}\;S \\ 2.52 \times 10^{28}\;S \\ infinite \end{array}$