In preparing a perpetual inventory card using first-in, first-out assume that you have inventory with the following cost date: 6 units @ $10 purchased on Jan. 1 and 10 units @ $11 purchased on Jan. 15. You sell 5 units for a retail sales amount of $20 each, what would be the cost of merchandise sold for these 5 units?

A.$50

B.$55

C.$100

D. $120