The rate constant for a first order reaction is 20 min^-1 . The time required for the initial concentration of the reactant to reduce to its $\frac{1}{32}$ level is ___ 10^-2 min.(Nearest integer) $\left(\begin{array}{r}\text{ Given }:\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\ln 10=2.303\\ \log 2\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}=0.3010\end{array}\right)$