$(10$ points$)$ Assume $($because it is not strictly true in the real world$)$ that an email address

consists of a non$-$empty string of letters and digits, followed by an $"$at$"$ sign $($@$),$ followed by a

machine name made up of a series of one or more non$-$empty strings of letters and numbers

separated by periods $(.)$ and terminated by either $".$com" or $".$edu" or $".$org". Write a BNF $($not

extended BNF$)$ description of such an email address.

Examples:

myself@cs$.$csustan.edu

$1579$@$17\mathrm{.}25\mathrm{.}20\mathrm{.}3.$org

Use:

$$ digit$>$ ::$=0|1|2|3|4|5|6|7|8|9$

$$ letter $>$::$=a|..|z|A|..|Z$

Start with:

$>$:$==$

$2$million$2$@hotmail.com

$2$bnot$2b$@ham.eggs.spam.edu