A certain pregnancy test is 98% effective in detecting an actual pregnancy. However, the test gives a "false positive" result for 2% of the non-pregnant women tested (i.e. if a woman is not pregenent and tries the test, the probability that the test will indicate pregnancy is 0.02). If 20% of women in a particular group are in fact pregnant, what is the probability that a women selected at random from this group is pregnant if the result is positive?