About 10% of Olympic athletes use illegal performance drugs. A test for the presence of these drugs shows up positive 90% of the time that drugs are present and shows up positive 20% of the time when...

About 10% of Olympic athletes use illegal performance drugs.  A test for the presence of these drugs shows up positive 90% of the time that drugs are present and shows up positive 20% of the time when drugs are not present (that is, given no drug use, the test shows positive with probability 0.2).

1. An athlete is selected at random and tested. What is the probability the test shows positive?

1. If the test turns out negative, what are the chances the athlete is actually clean (that is, not a drug user)?