4. Barnett Corporation uses the weighted-average method in its process costing system. The company adds materials at the beginning of the process in Department M. Conversion costs were 75% complete with respect to the 4,000 units in work in process at May 1 and 50% complete with respect to the 6,000 units in work in process at May 31. During May, 12,000 units were completed and transferred to the next department. An analysis of the costs relating to work in process at May 1 and to production activity for May follows: Work in process May 1. Costs added during May... Materials Conversion $13,800 $3,740 $42,000 $26,260 The total cost per equivalent unit for May was: A. $5.02 B. $5.10 C. $5.12 D. $5.25