1.Consider next the probability of E, P(E). Here we need more information. Because there are 36 possibilities in all, and the sum of their probabilities must equal 1, each singleton event {(a,b)} is assigned probability equal to 1/36. Because E is composed of 4 such distinct singleton events, P(E)=4/36= 1/9.
2. a similar argument we see that the probability that the first die rolls 1 and the second die rolls 3 is 1/36. The probability that the first die rolls 3 and the second die rolls 1 is also 1/36. Hence, the combination (1,3) is rolled with probability 2/36 = 1/18.
