6.71 Suppose that we define the following events:

C 5 event that a randomly selected driver is observed to be using a cell phone A 5 event that a randomly selected driver is observed driving a passenger automobile V 5 event that a randomly selected driver is observed driving a van or SUV T 5 event that a randomly selected driver is observed driving a pickup truck Based on the article “Three Percent of Drivers on Hand-Held Cell Phones at Any Given Time” (San Luis Obispo Tribune, July 24, 2001), the following probability estimates are reasonable:

PsCd 5 .03 PsCuAd 5 .026 PsCuVd 5 .048 PsCuTd 5 .019 Explain why PsCd is not just the average of the three given conditional probabilities.