Show that given any regular language L, then the set

L1 = {uv : u L, |v| = 2} is also a regular language.

Described in words, L1 is the set of all strings that can be obtained by joining two extra letters to the end of a string in L.

For simplicity, you can assume the underlying alphabet is = {a, b}. (But you should also think a bit about how you would phrase your argument for a more general alphabet.)