20. A certain factory operates three different shifts. Over the last year, 200 accidents have occurred at the factory.

Some of these can be attributed at least in part to unsafe working conditions, whereas the others are unrelated to working conditions. The accompanying table gives the percentage of accidents falling in each type of accident–

shift category.

P(Ar ¨ Br)

P(A ´ B)

P(Ar)

P(A) 1 P(B) 5 1 P(B) 5 .50 P(A) 5 .30 electric) 5 .005 P(all five purchase gas) 5 .116 Unsafe Unrelated Conditions to Conditions Day 10% 35%

Shift Swing 8% 20%

Night 5% 22%

Suppose one of the 200 accident reports is randomly selected from a file of reports, and the shift and type of accident are determined.

a. What are the simple events?

b. What is the probability that the selected accident was attributed to unsafe conditions?

c. What is the probability that the selected accident did not occur on the day shift?