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

Compounds '$\mathrm{A}$' and '$\mathrm{B}$' react according to the following chemical equation 

$\mathrm{A}\left(\mathrm{g}\right)+2 \mathrm{B}\left(\mathrm{g}\right)⟶2\mathrm{C}\left(\mathrm{g}\right)$

Concentration of either '$\mathrm{A}$' or '$\mathrm{B}$' were changed keeping the concentrations of one of the reactants constant and rates were measured as a function of initial concentration. Following results were obtained. Choose the correct option for the rate equations for this reaction.