A department adds raw materials to a process at the beginning of the process and incurs conversion costs uniformly throughout the process. For the month of January there were no units in the beginning work in process inventory; 90000 units were started into production in January; and there were 20000 units that were 40% complete in the ending work in process inventory at the end of January. What were the equivalent units of production for conversion costs for the month of January?

A) 70000 equivalent units.
B) 82000 equivalent units.
C) 78000 equivalent units.
D) 90000 equivalent units.

The equivalent units of production for conversion costs are the units that have been partially processed and still require further work in the ending work in process inventory, plus the units fully processed during the period.

Units fully processed during the period = 90000
Units partially processed in the ending work in process inventory = 20000 x 0.4 = 8000
Total equivalent units of production for conversion costs = 90000 + 8000 = 98000

However, this answer includes the units started but not completed in January. Since we only want to calculate the equivalent units of production for January, we need to subtract the units not completed in January:

Units not completed in January = (90000 - 20000) = 70000
Equivalent units of production for conversion costs in January = 98000 - 70000 = 28000

Therefore, the answer is C (78000 equivalent units).