Suppose that at some future time every telephone in the world is assigned a number that contains a country code $1$ to $3$ digits long, that is, of the form X, XX, or XXX, followed by a $10$-digit telephone number of the form NXX-NXX-XXXX $\text{(as described in Example} \: 8).$ How many different telephone numbers would be available worldwide under this numbering plan?
