Assume that the car lot contains 25 percent Porches, 35 percent BMWs, and 40 percent Volvos. Of the Porches, 20 percent have navigation systems, 90 percent of the BMWs have navigation systems, and 70 percent of the Volvos have navigation systems. You are assigned a car at random.
1) If the car has a navigation system, what is the probability that it is not a Porche?