Assume that the car lot contains 45 percent Porches, 30 percent Corvettes, and 25 percent Jaguars. Of the Porches, 40 percent have navigation systems, 30 percent of the Corvettes have navigation systems, and 50 percent of the Jaguars have navigation systems. Furthermore, 50 percent of the Porches, 80 percent of the Corvettes, and 70 percent of the Jaguars are silver. The property of being silver is independent from having a navigation system. You are assigned a car at random.

1) If the car has a navigation system and is silver, what is the probability that it is a Porche?