Seth is trying to decide how many workers is the optimal amount at his factory, which produces artisan-crafted grooming products. He observes the following:

When there is one worker, 10 hairbrushes are produced daily.
When there are two workers, 16 hairbrushes are produced daily.
When there are three workers, 20 hairbrushes are produced daily.
What is the marginal product of the third worker?