4 kg girl is standing on a 166 kg plank. The plank, originally at rest, is free to slide on a frozen lake, which is a flat, frictionless surface.

A 44.4 kg girl is standing on a 166 kg plank. The plank, originally at rest, is free to slide on a frozen lake, which is a flat, frictionless surface. The girl begins to walk along the plank at a constant velocity of 1.78i m/s relative to the plank. What is her and the planks velocity relative to the ice surface?