4. one in 2,000 people have a certain disease. there is a test for the disease that correctly diagnoses patients 99% of the time. in other words, the test is positive 99% of the time for patients with the disease, and it is negative 99% of the time for patients without the disease. if a randomly selected person tests positive for the disease, what is the chance he or she has the disease?

show work , i don't get how to do it.