Chapter 6, Problem 21RE

(a)

To determine

To calculate: The probability that a code word selected randomly begins with string ABC where a code word is of seven characters which is a combination of letters and digits where first three characters can be any letter or digit and last four characters must be a digit. For example, $\text{7A32765}$ is permissible, but $\text{7A3B765}$ is not.

(b)

To determine

To calculate: The probability that a code word selected randomly ends with $\text{6578}$ where a code word is of seven characters which is a combination of letters and digits where first three characters can be any letter or digit and last four characters must be a digit. For example, $\text{7A32765}$ is allowed, but $\text{7A3B765}$ is not.

(c)

To determine

To calculate: The probability that a code word selected randomly includes three letters followed by four even digits where a code word is of seven characters which is a combination of letters and digits where first three characters can be any letter or digit and last four characters must be a digit. For example, $\text{7A32765}$ is allowed, but $\text{7A3B765}$ is not.