Consider the CFG with S, A, B as the non-terminal alphabet, a, b as the terminal alphabet, S as the start symbol and the following set of production rules. S→bA S→aB A→a B→bA→a SB→b SA→b AAB→aBB. Which of the following string is generated by the grammar?
1) aabbbb
2) abbbba
3) aabbab
4) aaaabb