34. Coronado Industries produces flash drives for computers, which it sells for $20 each. Each flash drive costs $7 of variable costs to make. During April, 600 drives were sold. Fixed costs for April were $1800. How much does Coronados operating income increase for each $1000 increase in revenue per month?

a) $650.

b) $250.

c) $12000.

d) Not enough information to determine the answer.