An express train is moving with a velocity `v_1`. Its driver finds another train is movig on the same track in the same direction with velocity `v_2`. To escape collision, driver applies a retardation a on the train. The minimum time of escaping collision be

Options

A. `t=(v_(1)-v_(2))/(a)`
B. `t_(1)=(v_(1)^(2)-V_(2)^(2))/(2)`
C. Both (a) and (b)
D. None of these