The boy jumped from the boat at a speed of 4 m / s, while the boat acquired a speed of 1 m / s. What is the weight

The boy jumped from the boat at a speed of 4 m / s, while the boat acquired a speed of 1 m / s. What is the weight of the boat if the weight of the boy is 50 kg?

Since the speed of the boat after interaction is 4 times less, then its mass will be 4 times more M = 4m = 4 * 50 = 200 kg
Then we use the Law of conservation of momentum MV1 + mV2 = 0, before that the momentum of the boy-boat system was equal to 0
MV1 = -mV2 h “set a minus, as the boat began to move in the opposite direction.
M = mV2 / V1 M = 4m