An equilateral prism of mass m rests on a rough    horizontal surface with coefficient of friction $\mu$ . A horizontal force F is applied on the prism as shown. If the  coefficient of friction is sufficiently high so that the prism does not slide before toppling, the minimum force required to topple the prism is   

 

 

• A

  $\frac{ m g}{\sqrt{3}}$

• B

  $\frac{ m g}{4}$

• C

  $\frac{\mu m g}{\sqrt{3}}$

• D

  $\frac{\mu m g}{4}$