Bullets of $0.03\; kg$ mass each, hit a plate at the rate of $200$ bullets per second, with a velocity of $50\;ms^{-1}$ and reflect back with a velocity of $30\;ms^{-1}$. The average force acting on the plate, in newtons, is :

Question

( A ) 300
( B ) 180
( C ) 480
( D ) 120