Telephone area codes are three-digit numbers of the form XXX.
a. Originally, the first and third digits were neither 0 nor 1 and the second digit was always a 0 or a 1. How many three-digit numbers of this type are possible?
b. Over time, the restrictions listed in part (a) have been altered; currently, the only requirement is that the first digit is neither 0 nor 1. How many threedigit numbers of this type are possible?
c. Why were the original restrictions listed in part (a) altered?
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