Please do no. 20 and 17 please

17. Use the exhaustive search parsing method to parse the string abbbbbb with the grammar in Example 5.5. In general, how many rounds will be needed to parse any string w in this language? 18. Is the string aabbabab in the language generated by the grammar S ass(b? 19. Show that the grammar in Example 1.14 is unambiguous. Prove the following result. Let G = (V,T, S, P) be a context-free grammar in which every AEV occurs on the left side of at most one production. Then G is unambiguous. 20