The Aluminum Company of America left parenthesis Alcoa right parenthesis has faced limited competition in the market for aluminum. Part 2 What barrier has kept new firms from entering the market for aluminum? Part 3 The Aluminum Company of America left parenthesis Alcoa right parenthesis Part 4 A. has had a patent on aluminum. B. has had almost exclusive ownership of bauxite, which is a key input. C. has enjoyed economies of scope from producing multiple types of products. D. has had lower long-run average costs than competitors. E. has been able to convince customers that its brand of aluminum has extra value