Which of the following meet the economist's definition of a "public good"? Explain why or why not in each case. a) National defense [2 points] b) A government-run swimming pool [2 points] c) The Nauset Beach lighthouse on Cape Cod [2 points] d) Route 93 North during rush hour [2 points] e) The public transit system in Boston (a.k.a, the "T") [2 points]