Hall Corporation uses the weighted-average method in its process costing system. Data concerning the first processing department for the most recent month are listed below: Beginning work in process inventory: Units in beginning work in process inventory. Materials costs.. Conversion costs.. 500 $7,700 $2,900 Percent complete with respect to materials... 75% Percent complete with respect to conversion. 25% Units started into production during the month 6,700 Units transferred to the next department during the month.. 5,900 $108,600 $121,000 Ending work in process inventory: 1,300 65% 40% Materials costs added during the month... Conversion costs added during the month. Units in ending work in process inventory. Percent complete with respect to materials.. Percent complete with respect to conversion. The cost per equivalent unit for conversion costs for the first department for the month is closest to: Select one: O a. $20.27 O b. $19.30 c. $18.85 O d. $17.21