Using only your text as reference (use of outside source will result in a zero grade) specifically use the Appendix to the chapter:

a. From an economic perspective, what are the marginal benefits of private sector unions in the U.S.?

b. From an economic perspective, what are the marginal costs of unions in the U.S.?

c. Do the marginal benefits exceed the costs? Why or why not?

Note that this is a societal level marginal analysis, so your costs and benefits must be societal level. Also, marginal costs are the opportunity costs which you need to identify. Also Note: Do not address public unions as the dynamics are different and not covered in the text.