Please help me answer these im stuck!

1. The inventor and manufacturer of Drug X has a patent on this medicine, but the patent will expire soon. Use the supply-and-demand model to explain verbally and illustrate graphically how the equilibrium price and quantity of drug X will change when the patent expires and other firms start producing and selling it. (8)4. Suppose that the doodad market has only 5 firms, each of which has 20% market share. a. What market structure is this? (1) b. If two of the firms in this market merge to form one firm with 40% market share (and the other three firms each maintain their 20% market share), how will concentration in the doodad market, as measured by HHI, change? Show the necessary calculations and explain if this merger would cause the DOJ change their "rating" of the level of market concentration? (3)