Please see the attached file.

A 1.00 x 102 kg crate is being pusehd across a horizontal floor by a force P that makes an angle of 30.0 degrees below the horizontal. The coefficient of kinetic friction is 0.200. What should be the magnitude of P, so that the net work done by it and the kinetic frictional force is zero?

Normal reaction = N = mg = 100*9.81 = 981 N
Kinetic friction force = ??????????????????????
This should be equal to the horizontal component of the force P.
Therefore, Pcos(300) = 196.2
Or P = 196.2/cos(300) = 226.55 N