mine was 4. why is everyboy referring to equations. didnt we have use the tabular approach.. at 5th bach the marinal revenue went negative. so my answer was 4 . and then i rechecked with 3, and 4 batches to confirm the answer.
i didnt do any adjustment for overtime but accounted for that when evaluating performance of production manager. revised hours were 3.25 which i used..