The Accompanying Table Below Shows How Total Donations, Average Donations, Total

Multiple Choice

The accompanying table below shows how total donations, average donations, total labor costs and average labor costs vary depending on the number of employees State U hires for its fundraising activities.  
The marginal benefit (in terms of extra donations) of the 2ⁿᵈ employee is:

A) $42,426.
B) $21,213.
C) $12,426.
D) $11,337.