Can you please explain the concept(s) related to each requirement and why in requirement "b" the "Completed and Transfer

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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.