In the pulley arrangement shown, the pulley ${\text{P}}_2$ is movable. Assuming coefficient of friction between m and surface to be $\mathrm{\mu }$, the minimum value of M for which m is at rest is

 

• A

  $\mathrm{M} = \frac{\mathrm{\mu m}}{2}$

• B

  $\mathrm{m} = \frac{\mathrm{\mu M}}{2}$

• C

  $\mathrm{M} = \frac{\mathrm{m}}{2\mathrm{\mu }}$

• D

  $\mathrm{m} = \frac{\mathrm{M}}{2\mathrm{\mu }}$