1. Health officials have suggested that the spread of AIDS in Houston can be partly contained if more males used condoms while engaging in sexual intercourse.
   1. What is the phenomenon called?
   2. Explain, and on an appropriate diagram, show why the number of condoms sold in Houston is likely to be lower than the optimal number.
   3. Explain 4 ways the government might promote a more optimal use of condoms.

1. Inoculation programs against certain diseases such as small pox, polio, and whooping cough would create what economic phenomenon?
   1. Provide an explanation for the concept mentioned in a) above
   2. What can the government do to intervene?
   3. Support your explanation above with graphs.