The probability mass function of the number of calls taken by a switchboard within 1 minute is

Question:

The probability mass function of the number of calls taken by a switchboard within 1 minute is given in Figure 2.77.

(a) Compute and sketch the cumulative distribution function of the number of calls taken within a minute.
(b) What is the expected number of calls taken within a minute?
(c) What is the variance of the number of calls taken within a minute?
(d) If the numbers of calls taken in two different minutes are independent, what are the expectation and variance of the number of calls taken within one hour?

Distribution
The word "distribution" has several meanings in the financial world, most of them pertaining to the payment of assets from a fund, account, or individual security to an investor or beneficiary. Retirement account distributions are among the most...