The number of phone calls coming into a telephone switchboard during each minute was recorded during an entire hour. During 30 of the 1-minute intervals there were no calls, during 20 intervals there was one call, and during 10 intervals there were two calls. A 1-minute interval is to be selected at random and the number of calls noted. Let X be the outcome. Then, X is a random variable taking on the values 0, 1, and 2.

(a) Write out a probability table for X.

(b) Compute E(X ).

(c) Interpret E(X ).