I've been trying to figure this problem out, but I can't find an answer that corresponds with the answer key. I have no sources but the internet to ask for help, as I am studying on my own.
Here's the problem (please provide a thorough and lucid explanation. I am very new to this and struggle to understand):
The telephone company has run out of seven digit telephone numbers for an area code. To fix this problem, the telephone company will introduce a new area code. Find the maximum number of new seven-digit telephone numbers that can be generated for the new area code if both of the following conditions must be met:
-The first digit cannot be 0 or 1
-The first three digits cannot be the emergency number 911 or the number 411 used for information
Thank you in advance for helping me! If you're willing to do something extra, please give me tips and sources to help me understand " Counting and Probability of Compound Events "