The time in which a force of 2 N produces a change of momentum of `0.4kg-ms^(-1)` in the body is

A body of mass 2kg is projected from the ground with a velocity 20ms^(-1) at an angle 30^(@) with the vertical. If t_(1) is the time in seconds at which the body is projected and t_(2) is the time in seconds at which it reaches the ground, the change in momentum in kgms^(-1) during the time (t_(2)-t_(1)) is