22.5 This exercise concerns grammars for very simple languages.

a. Write a context-free grammar for the language a"b".

b. Write a context-free grammar for the palindrome language: the set of all strings whose second half is the reverse of the first half.

c. Write a context-sensitive grammar for the language a"b"c".

d. Write a context-sensitive grammar for the duplicate language: the set of all strings whose second half is the same as the first half.