The output of workers at a factory depends on the number of supervisors hired (see below). The factory sells its output for $0.50 each; it hires 50 production workers at a wage of $100 per day, and needs to decide how many supervisors to hire. The daily wage of supervisors is $500 but output rises as more supervisors are hired, as shown below. How many supervisors should it hire?

Supervisors Output (units per day)

0 11,000

1 14,800

2 18,000

3 19,500

4 20,200

5 20,600