Can someone please explain why that's the answer. Please show all work. Greatly appreciated!

2) In the month of June, a department had 20,000 units in beginning work in process that were 70% complete. During June, 90,000 units were transferred into production from another department. At the end of June there were 10,000 units in ending work in process that were complete. Materials are added at the beginning of the process, while conversion costs are incurred uniformly throughout the process. The equivalent units of production for conversion costs for June were a. 90,000 equivalent units. b. 104,000 equivalent units. c. 100,000 equivalent units. d 110,000 equivalent units