What are the steps on solving this?

The figure shows a block of mass m=4kg being pushed to the right across a ceiling by a force of magnitude P=50N which makes an angle 0 - 70 with respect to the horizontal. If the block has an acceleration of magnitude a=2.7 m/s2 which is directed to the right, what is the coefficient of kinetic friction /k? (A) 0.3 AP (B) 0.5 (C) 0.8 (D) 0.4 (E) 0.9