Lofty Airlines has a flight for which the regular ticket price is $200 and the variable costs per passenger are $50. Fixed costs assigned to each flight are $12,000. Each flight has a capacity of 125 seats, with an average of 95 seats sold at the regular price. To attract customers to the last 30 unsold seats, Lofty discounts the tickets by 50% for standby passengers. The contribution margin per standby passenger is

a. $25

b. $150

c. $100

d. $50