The Solution is 100% right. I just need step by step explanation Please explain each step I really do not know anything here.

2. Consider the class REGA of all regular languages over the fixed one-letter alphabet A={a} (a) Is REGA countable? (b) Is the class NOTREG of all languages over A that are not regular countable? (c) Is the class REGANNTREGA countable? For each question, you must give a precise argument substantiating your answer. 2 (a) REGA is an regular language if it is accepted by a SFF, and we know If we tave a DYF A over fixed alphabeta A={a} which are m in number and 2fa has n statec. Then, go to number of combination possible for Dn+0 is 2nnmn which is countable REGA in finite as regular language which is determined by using oL +a. REGA is coustable. (b) A is countable infinite 2A is also counctable infinite REGA is finite 27 2AREGA is infinite NOTREGA is uncountable (c): REGA NOTREGA ={} lt is counctable