An object of mass 10 kg moves at a constant speed of 10 ms⁻¹. A constant force that acts for 4 s on the object gives it a speed of 2 ms⁻¹ in the opposite direction. The magnitude of force acting on the object is (Take the direction of initial velocity as positive)

A. 3 N
B. 30 N
C. 300 N
D. 0.3 N