Can you please explain the concept(s) related to each requirement and why in requirement "b" the "Completed and Transferred units" is 227,000, i.e. why is 215,000 from requirement "a" is considered?

Sodius Chemical Inc. placed 220,000 liters of direct materials into the mixing process. At the end of the month, 5,000 liters were still in process, 30% converted as to labor and factory overhead. All direct materials are placed in mixing at the beginning of the process and conversion costs occur evenly during the process. Sodius uses weighted-average costing.

Required:

a. Determine the equivalent units in process for direct materials and conversion costs, assuming there was no beginning inventory.

b. Determine the equivalent units in process for direct materials and conversion costs, assuming that 12,000 liters of chemicals were 40% complete prior to the addition of the 220,000 liters.