Buskirk Construction buys on terms of 2/15, net 60 days. It does not take discounts, and it typically pays on time, 60 days after the invoice date. Net purchases amount to $500,000 per year. On average, how much "free" trade credit does the firm receive during the year? (Assume a 365-day year, and note that purchases are net of discounts.)

a. $19,315

b. $16,644

c. $18,699

d. $20,548

e. $24,863