$3.$ Let $\backslash$Sigma $=\{$a$,$ b$\}$ and A $=\{$w $|$ baab is a substring of w and abba is not a substring of w$\}.$

Is A a regular language? Justify your answer. You will probably need a proof by contradiction with the pumping lemma. But keep in mind that the lemma states there exists a split for all strings, so you cannot just choose $1$ string and then show $1$ split and how the pumping up$/$down does not work $($need to show all cases for whichever string$).$