A small indigenous village is situated along the banks of a river. For this year, they need to decide how much water to collect from the river for irrigation purposes. The amount of water that is collected this year has no bearing on the amount of water that they can collect in future years from the river. Marginal Social Benefits from the water are given by: MSB = 20-q/2. Marginal Social Costs from collecting the water are given by: MSC = 2 + q.