1. The probability of a dry summer is equal to 0.2, the probability of a wet summer is equal to 0.3, and the probability of a summer with normal precipitation is equal to 0.5. A climatologist observed the precipitation during four consecutive summers.

a). Enumerate the sample space, and assign probabilities to each elementary event;

b). What is the probability of observing two dry summers?

c). What is the probability of observing at least two dry summers?

d). What is the probability of not observing a wet summer?