$1.$ Build a regular expression that captures all non$-$empty sequences of letters other than the

string $$aaa$.$ For your convenience, you may use a $$not$$ operator that takes a set of letters

as argument and matches any other letter. For instance, not$($abc$)$ matches any letter other

than a$,$ b and c$.$ Use $.$ to match any letter.

$2.$ Build a regular expression that captures all Media Access Control Addresses $($MAC address$)$

which is a $12$ digit hexadecimal where each pair of hexadecimal numbers is separated by

a colon or hyphen. Additionally, MAC address is also valid where three groups of four

hexadecimal digits are separated by dots$(.)$ Make sure you support your answer with proper

reasoning. Here are some of the MAC addresses that your regex should match $($this list is

not exhaustive$).$

Keep in mind Hexadecimal numbers range $0$ to $9$ and letters from a to f and A

to F

$01-23-45-67-89-$AB

$01$:AB:$45$:CD:$89$:EF

$0123\mathrm{.}4567\mathrm{.}89$AB