Q$1)$ Let $=a,b$

$(21$ Points$)$

a$)$ Build an FA that accepts only those words that do

not end in $ab.$

b$)$ Build an FA that accepts only the language of all

words with $b$ as the second letter. Find the regular

expression for the language.

c$)$ Build an FA that accepts only those words that have

more than four letters.

d$)$ Build an FA that accepts only those words that have

fewer than four letters.

e$)$ Build an FA that accepts only those words with

exactly four letters.

f$)$ Build an FA that accepts only those words that begin

or end with a double letter.