Penny, Inc. employs a process costing system. Direct materials are added at the beginning of the process. Here is information about July’s activities:

On July 1:
Beginning inventories 850 units, 60% complete
Direct materials cost $5,000
Conversion costs $4,000
During July:
Number of units started 15,000
Direct materials added $155,000
Conversion costs added $83,520
On July 31:
Ending inventories 1,600 units, 40% complete

Using the FIFO method, the cost per equivalent unit for materials used during July was

a. $9.78
b. $10.33
c. $10.78
d. $10.65