How Does Throwing a Parcel Affect the Speed of a Trolley?

[Procrastinate]

A man of mass 80kg (m₁) stands on a trolley of mass 120kg (m₂) and throws a parcel of mass 10kg (m₃) with a velocity of 4.0ms^-2 (u₂) horizontally away from the rear of the trolley. What is the speed with which the trolley and the man commence to move?

I am just wondering whether the initial velocity of the man and the trolley is zero? I can only seem to work out the correct answer if it is zero because I can't solve for two variables.

(m₁+m₂)u + m₃u₂ = (m₁+m₂)v

200 x 0 + 40 = 200v
40 = 200v
0.2ms^-1 = v

 

[ideasrule]

The initial velocity is assumed to be 0, yes.