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Homework Assignment 13 4.4 HW

Current rules for telephone area codes allow the use of digits​ 2-9 for the first​ digit, and​ 0-9 for the second and third​ digits, but the last two digits cannot both be 1​ (to avoid confusion with area codes such as​ 911). How many different area codes are possible with these​ rules? That same rule applies to the exchange​ numbers, which are the three digits immediately preceding the last four digits of a phone number. Given both of those​ rules, how many​ 10-digit phone numbers are​ possible? Given that these rules apply to the United States and Canada and a few​ islands, are there enough possible phone​ numbers? (Assume that the combined population is about​ 400,000,000.)