Both Google and Facebook make their money by charging advertisers to run their ads, and the bigger an audience they have, the more they can charge.

Currently ____________ people are enrolled in PreCheck and more than __________ more have PreCheck clearance through Global Entry, the Customs and Border Protection trusted-traveler program.

Fill in the blank(s) with the appropriate word(s).

Assume that an association of young workers has lobbied Congress to require that all workers retire once they reach the age of fifty. What impact would this law have on the nation's production possibilities frontier?

A) no impact at all B) The level of unemployment would decrease so the production possibilities frontier would shift outward. C) The nation would move to a new position on its production possibilities frontier but the frontier itself would not shift. D) The production possibilities frontier would shift inward. E) The number of young workers would increase so the production possibilities frontier would shift outward.