please help me answer this question. ty a lot

Question 3 (2.5 points) Suppose De Beers is behaving like a monopoly and faces the demand curve 20 + 200 and have a marginal cost curve such that MC = 20Q where Q is the output level and P is the price. As more alternatives become available and De Beers lose market share, what will happen to the demand curve faced by De Beers? Suppose the new demand curve is P = -20Q* + 3000 Suppose average total cost, ATC = 40Q + 0. 5Q4, what is the quantity that De Beers produce now and what is its profit under this monopolistic competition market structure? Explain your answers