A 30 kg box has to move up an inclined plane of slope 30° to the horizontal with a uniform velocity of 5 ms^-1.If the frictional force retarding the motion is 150N, the horizontal force required to move the box up is(g=10ms^-2)

• A

  $300\times \frac{2}{\sqrt{3}}\mathrm{N}$

• B

  $300\times \frac{\sqrt{3}}{2}\mathrm{N}$

• C

  300N

• D

  150N