A body of mass m1 moving with an unknown velocity of v1^i, undergoes a collinear collision with a body of mass m2 moving with a velocity v2^i. After collision, m1 and m2 move with velocities of v3^i and v4^i, respectively.
If m2=0.5 m1 and v3=0.5v1 then v1 is equal to,