Brody Corp uses a process costing system. Beginning inventory for January consisted of 1,000 units that were 40% completed. 10,000 units were started into the process during January. On January 31, the inventory consisted of 500 units that were 70% completed. How many units were completed during the period?

a. 11,000

b. 10,500

c. 11,500

d. 9,500