The rate of a first-order reaction is 0.04 mol l^-1 s^-1 at 10 seconds and 0.03 mol l^-1 s^-1 at 20 seconds after initiation of the reaction. The…

The rate of a first-order reaction is $\displaystyle 0.04 \mathrm{~mol} \mathrm{l}^{-1} \mathrm{~s}^{-1}$ at $\displaystyle 10$ seconds and $\displaystyle 0.03 \mathrm{~mol} \mathrm{l}^{-1} \mathrm{~s}^{-1}$ at $\displaystyle 20$ seconds after initiation of the reaction. The half-life period of the reaction is :