A block of mass m, lying on a rough horizontal plane, is acted upon by a horizontal force P and another force Q inclined at an angle q to the vertical. The block will

remain in equilibrium, if the coefficient of friction between it and the surface is

• A

  $(\mathrm{P}+\mathrm{Qsin}\mathrm{\theta })/(\mathrm{mg}+\mathrm{Qcos}\mathrm{\theta })$

• B

  $(\mathrm{Pcos}\mathrm{\theta }+\mathrm{Q})/(\mathrm{mg}-\mathrm{Qsin}\mathrm{\theta })$

• C

  $(\mathrm{P}+\mathrm{Qcos}\mathrm{\theta })/(\mathrm{mg}+\mathrm{Qsin}\mathrm{\theta })$

• D

  $(\mathrm{Psin}\mathrm{\theta }-\mathrm{Q})/(\mathrm{mg}-\mathrm{Qcos}\mathrm{\theta })$