156 A sample space consists of four sample points S1, S2, S3, and S4, where P(S12 = .2, P(S22 = .1, P(S32 = .3, and P(S42 = .4.

a. Show that the sample points obey the two probability rules for a sample space.

b. If an event A = 5S1, S4,6 find P(A).