How to solve

The following data were taken from the accounting records of a company that uses the Weighted Average method in its process costing system:

Beginning work in process inventory: $20,000$ units $($materials $100\%$ complete, conversion costs $60\%$ complete$)$

Started in process during the period: $80,000$ units

Ending work in process inventory: $30,000$ units $($materials $100\%$ complete, conversion costs $70\%$ complete$)$

The equivalent units are

materials, $80,000$ units; conversion costs, $91,000$ units.

materials, $100,000$ units; conversion costs, $91,000$ units.

materials, $100,000$ units; conversion costs, $79,000$ units.

materials, $80,000$ units; conversion costs, $79,000$ units.