2. (10 points in total, 5 for each) Suppose that a certain disease is present in 10% of the population, and that
there is a screening test designed to detect this disease if present. The test does not always work perfectly.
Sometimes the test is negative when the disease is present, and sometimes it is positive when the disease is
absent. The test accuracy table below shows the proportion of times that the test produces various results. 
(a). Use the definition of conditional probability to find P(D|N).