Suppose Charles owns a lawn-mowing company. Assume that without workers, no yards are mowed. When he hires one worker, he is able to mow 2 yards per day. With two workers, he can mow 5 yards per day, and with three workers, he can mow 10 yards per day. The marginal product of the first worker is yards per day. The marginal product of the second worker is yards per day. Last, the marginal product of the third worker is | yards per day. The marginal product of labor potentially increases (from one to three workers) due to