Answer: b. MB > MC or until they are equal.
Step-by-step explanation:
It is best that Frieda produces bread at the level where Marginal benefits exceeds marginal costs. The difference will keep giving her more profit.
She should keep increasing her production so long as the Marginal benefit exceeds marginal cost but should stop at the level where the Marginal benefit and marginal cost become equal because producing past this point would mean that she would incur a marginal loss on each unit.