Answer:
50 guests
Explanation:
Marginal product is the factor of production, which is defined as the change in the output results or consequence from employing one or single unit of a specific unit. It is also acknowledge as the marginal physical productivity.
For example, the change in the output results when the business or the firm increase the labor from 6 to 7. So, 1 would be the marginal product.
So, in this case, the marginal product for the third waiter is 50 guests (120 - 70).