Holly's Ham, Inc. sells hams during the major holiday seasons. During the current year 11,000 hams were sold resulting in $220,000 of sales revenue, $55,000 of variable costs, and $24,000 of fixed cost. How many units must be sold to make $63,000?

a. 5,800
b. 17,400
c. 4,320
d. 3,600