Answer:the correct answer is A. For the 11th worker, the marginal profit is $600.
Step-by-step explanation:
10 men 20 vanities per week
11 men 22 vanities per week
1 man more 2 vanities more
If the company uses 1 man more produces 2 vanities more, so the company spends $1000 on the extra man and makes 2*$800= $1,600 (for two extra vanities). For the 11th worker, the marginal profit is = $1600-$1000= $600