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

The 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 2^nd employee is:

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