help me work through this

Assume there are three partnering countries who control all of the world's supply of oil. Inverse demand for oil is given by the equation P = 100 2Q, where P is the per-unit price of oil and Q is the quantity. Marginal costs are identical across countries at $20 per unit of oil. These three partnering countries form a cartel and act as a monopolist to maximize profits. What quantity do they choose? | What per-unit price do they set? $ | If they split profit three ways, what is the individual profit of each country? $ | (Round to two decimals if necessary.)