$.$ For a Batch reactor with an initial concentration $Ca=1mo\frac{l}{1}$ calculate the time required to reduce $Ca$ to $40\%$ of initial value, $k=0\mathrm{.}2mi{n}^{-1}.$ Assume first order reaction.

Use: ${\displaystyle \underset{0}{\overset{x}{}}}\frac{dx}{1-x}=(ln(\frac{1}{1-x}){]}_0^x.$