Answer to Question #47611 in Engineering for RKOSAMIA

Question

Standard telephone keypads contain the digits zero through nine. The numbers two through nine each have
three letters associated with them. Many people find it difficult to memorize phone numbers, so they use the
correspondence between digits and letters to develop seven-letter words that correspond to their phone
numbers. For example, a person whose telephone number is 686-2377 might use the correspondence
indicated in Fig. 7.29 to develop the seven-letter word “NUMBERS.” Every seven-letter word corresponds to
exactly one seven-digit telephone number. A restaurant wishing to increase its takeout business could surely
do so with the number 825-3688 (that is, “TAKEOUT”)