Bill14564 has the right idea very simple to set up.
Trying to block every number in an area code you may not want good luck.
How many 7 digit numbers are possible in a single area code?
8,000,000
= 8,000,000. Therefore, according to the condition that the first digit cannot be either 1 or 0, we can have 8,000,000 possible ways of creating a seven-digit area code.
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