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). a. 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, b. 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.)
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). a. 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, b. 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.)
please explain part b
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