
In equilibrium of block $B$ implies $T=M g \ldots(i)$
If block $A$ does not move, then $T=f_{s}$
where $f_{s}=$ frictional force $=\mu_{S} N=\mu_{s} m g$
implies $T=\mu_{s} m g \ldots(i i)$
Thus, from Eqs. $( i )$ and $(ii),$ we have
$M=\mu_{s} m g$ or $M=\mu_{s} m$
Given: $\mu_{s}=0.2, m=2 k g$
$\therefore M=0.2 \times 2=0.4 k g$





