i need help with this

4. Suppose that a free medical test for a certain disease is available. This test is 90% reliable in the following sense: If a person has the disease, there is a probability of 0.9 that the test will correctly indicate that the person has the disease (a true positive); whereas, if a person does not have the disease, there is a probability of 0.1 that the test will incorrectly indicate that the person has the disease (a false positive). In addition, suppose that this disease is rare in the sense that there is only a 1 in 10,000 chance that you have the disease. Suppose that, on a whim, you decide to take the test and when the results come back the test indicates that you have the disease! With this additional information how much does the probability that you actually have the disease increase? (a) 1/10008 (b) 9/10000 (c) 9/10008 (d) 1/10000 (e) None of the above