일반물리학 1 — Center of Mass and Linear Momentum: Problem 16

16 Ricardo, of mass 80 kg, and Carmelita, who is lighter, are enjoying Lake Merced at dusk in a 30 kg canoe. When the canoe is at rest in the placid water, they exchange seats, which are 3.0 m apart and symmetrically located with respect to the canoe’s center. If the canoe moves 45 cm horizontally relative to a pier post, what is Carmelita’s mass?