M1 - momentum on a slope

Two particles A and B, of masses 0.3kg and 0.2 kg respectively, are moving freely along a line of greatest slope of the plane when they collide at a point 4m from the bottom of the plane. Immediately before the collision A is moving up the plane at a speed of 2m/s and B is moving down the plane with a speed of 1.5 m/s. Immediately after the collision A is instantaneously at rest. Find:

a) time taken by A, from the instant of the collision to reach the bottom of the plane
I worked this out to be 3.95s which is correct.

b) the speed with which B starts to move up the plane after the collision.
Here is where I got stuck. I thought you could use the principle of the conservation of momentum which would be:

2(0.3) - 1.5(0.2) = 0.2v
This gives v=1.5m/s but the answer is 15m/s ?

c)the total distance travelled by B, from the instant of the collision until the instant is reaches the bottom of the plane.

have you considered the possibility of a typo?

yeah i was thinking that! However, say my answer was right and it was 1.5 m/s, how would you do c) ?

very easily...
simple kinemtics