A block of mass m = 3kg resting on a horizontal friction less floor is horizontally struck by a 9N force that acts for 0.02 sec. After 3 sec it receives a second **** of force 9N but in opposite direction which acts for 0.01 sec. The speed of the body after 30 sec. is
(A) 0
(B) 3 cm/sec
(C) 90cm/sec
(D) 30 cm/sec
