Department X of a manufacturing company works on only one product, and all costs are incurred uniformly as the product goes along the assembly line. The 10,000 units in process on December 1 were 78% completed. An additional 36,000 units were placed in production during December. On December 31, the 20,000 units in process were 52% completed. The equivalent units of production during December amounted to:

a)31,200.

b) 66,000.

c) 53,400.

d) 73,400.