How does process costing differ from job order costing? When is process costing used instead of job-order costing? Can a company simply choose one method over the other because it likes one method better? Which two types of product costs are typically added together in process costing? Why are they combined? What are equivalent units? Under the weighted-average method, are the beginning or ending percentages of completion used?Why? Should the total percentages of completion add to 100 %? Why or why not