In a first order reaction,the concentration of the reactant decreases from 0.02M to 0.005M in 10min.The time taken to change the concentration of reactant from 0.16M to 0.025M

Question

$\begin{array}{1 1}(a)\;10min&(b)\;20min\\(c)\;40min&(d)\;30min\end{array}$