Realm Companys budget indicates that 16,000 units are to be sold during September. If the company has 4,000 units on hand at the beginning of the period and plan to have 6,000 units on hand at the end of the period at the end of the month, how many units should be produced during the month?

A. 22,000

B. 18,000

C. 14,000

D. 16,000