I just have general questions about sets and determining if they are regular languages.
i) If A is regular, and A is a subset of B, then B must be regular.
ii) If B is regular, and A is a subset of B, then A must be regular.
iii) If A and AB are regular, than B must be regular
iv) If Ai is an infinite family of regular sets, than the union of all those sets is regular.
For the third one, I know that AB can only be regular if B is regular, because a regular set * a irregular one is not regular.
Lost for the other ones.