The Assembly Department of Smart Computers had 500 units of beginning inventory in the month of September and 2,000 units were transferred to it from the Production Department. The Assembly Department completed 1,000 units during the month and transferred them to the Packaging Department.

Calculate the total number of units to account for by the Assembly Department.

A) 1,500 units

B) 2,000 units

C) 500 units

D) 2,500 units