Many firms require their employees to be screened for drugs. Some employees are concerned that a false positive may be recorded from the screening; that is, employees who are not drug abusers may incorrectly test positive. Assume that 10% in a particular population are drug abusers. Suppose that the probability of a false positive is 0.5% and that the probability of a correct positive on someone who is under the influence of drugs is 99.9%. What is the probability that a person who tests positive is really a drug abuser?