Roary Chemicals has a mixing department and a refining department. Its process-costing system in the mixing department has two direct materials cost categories (Chemical P and Chemical Q) and one conversion costs pool. The following data pertain to the mixing department for July 2015:

Chemical P is introduced at the start of operations in the mixing department, and Chemical Q is added when the product is three-quarters completed in the mixing department. Conversion costs are added evenly during the process. The ending work in process in the mixing department is two-thirds completed.

Required
1. Compute the equivalent units in the mixing department for July 2015 for each cost category.
2. Compute (a) the cost of goods completed and transferred to the refining department during July and (b) the cost of work in process as of July 31, 2015.
3. Would there be any difference in your calculations of equivalent units if you used a weighted average approach versus the FIFO approach? What is the reason for this?