It is well known that steroid usage is banned in athletes. As a result, athletes are randomly tested. The steroid test procedures are believed to be equally effective on both steroid users as well as non-steroid users. The effective rate is 98%. Assume 90% of the athletes are clean (not steroid users). Suppose an athlete is tested as a steroid user (and thus could be disqualified from the Summer Olympics games), what is the probability that the athlete is actually clean (i. e., not a steroid user)