$A$ block of mass $8 \ kg$ is suspended by a rope of length $3 \ m$ from the ceiling. $A$ force of $40 \ N$ is applied horizontally to the block. Then the angle that the rope makes with the vertical in equilibrium is (acceleration due to gravity $= 10 \ m \ s^{-2}$,neglect the mass of the rope).

• A
  $\sin ^{-1}\left(\frac{1}{2}\right)$
• B
  $\tan ^{-1}\left(\frac{1}{2}\right)$
• C
  $\sin ^{-1}\left(\frac{1}{3}\right)$
• D
  $\tan ^{-1}\left(\frac{1}{3}\right)$