A 20.0kg sled holding a 42.0kg child has a speed of 3.50m/s. they collide with and pick up a snowman,…

A 20.0kg sled holding a 42.0kg child has a speed of 3.50m/s. they collide with and pick up a snowman, initially at rest. the resulting speed of the snowman, sled, and child is 2.90m/s. what is the snowmans mass?