"In America, what proportion of all businesses are (a) proprietorships, (b) partnerships, (c) private companies, and (d) public companies? Provide an example of an industry that has a large share of proprietorships. Why is this the case? Provide an example of an industry that has a large share of partnerships. Why is this the case? Provide an example of an industry that has a large share of private companies. Why is this the case? Provide an example of an industry that has a large share of public companies. Why is this the case?"