(i) Leftmost derivation
Consider
S => SAS
S => bAS (as S => b)
S => bbaS (as A => ba)
S => bbaSAS (as S => SAS)
S => bbabAS (as S => b)
S => bbabbS (as A => b)
S => bbabbSAS (as S => SAS)
S => bbabbbAS (as S => b)
S => bbabbbbaS ( as A => ba)
S => bbabbbbab (as S => b)
(ii) Rightmost derivation
Consider
S => SAS
S => SAb (as S => b)
S => Sbab (as A=> ba)
S => SASbab (as S => SAS)
S => SAbbab (as S => b)
S => Sbbbab (as A => b)
S => SASbbbab (as S => SAS)
S => SAbbbbab (as S => b)
S => Sbabbbbab (as A => ba)
S => bbabbbbab (as S => b)
(iii) Parse tree