The LHS non-terminal S is defined as non-terminal A, terminal a, non-terminal B and terminal b, where non-terminal A can be zero or more b’s or one b, and where non-terminal B can be one or more a’s or one a;
Resulting in one or more b’s or one b, one a, one or more a’s or one a, and one b.
Answers a (baab) and d (bbaab) adhere to this production.