The rate constant of a reaction at 500 K and 700 K are $$0.02 \mathrm{~s}^{-1}$$ and $$0.2 \mathrm{~s}^{-1}$$ respectively. The activation energy of the reaction (in $$\left.\mathrm{kJ} \mathrm{mol}^{-1}\right)$$ is $$\left(R=8.3 \mathrm{JK}^{-1} \mathrm{~mol}^{-1}\right)$$

The time required for completion of $$93.75 \%$$ of a first order reaction is $$x$$ minutes. The half-life of it (in minutes) is