Ricardo (R) and Maria (M) are in a canoe that is stationary and floating on a calm lake. They are 4.0 m apart, symmetrically located about the center of the canoe as shown in the figure on the left. Ricardo has mass 87.1 kg, and the canoe is massless. The canoe is free to move in the water without friction.
Ricardo and Maria both move to the center of the canoe. Ricardo notices that the canoe moves a distance d = 0.37 m relative to a rock that is stationary in the water. What is Maria's mass in kg?