A company produces flash drives for computers, which it sells for $20 each. Each flash drive costs $13 of variable costs to make. During April, 1,000 drives were sold, Fixed costs for March were $2 per unit for a total of $2,000 for the month. How much is the contribution margin ratio? Select one: O a. 65% O b. 25% O c. 35% O d. 75%