4. Convert the following regular expressions to NFAs. (a) aabb)* Ub (9 pt) (b) at u(ab)+ (8 pt) (c) (au b)+a+b+ (8 pt) Note: The U operator above is the + operator for regular expressions that we defined in class. On the other hand, the + operator in the exponents in parts (a) and (b) is different; it is a closure operator. That is, at means one or more a