In figure coefficient of friction between m₁ and m₂ is $\mathrm{\mu }$ and that between m₁ and the wall is zero. A force F is pressing the system against the wall. Minimum value of force required to hold the system in equilibrium is:

• A

  ${\mathrm{\mu m}}_1\mathrm{g}$

• B

  ${\mathrm{\mu m}}_2\mathrm{g}$

• C

  $\text{μ}\left(m_1+m_2\right)g$

• D

  system cannot be held in equilibrium