How for I know what step gets allocated first in the step down method? All of the practice questions hinge on what you do first, but the text doesn't explain how you know which one should happen first.

Question: Assume the October Company has three service departments, S1(engineering), S2 (materials handling) and S3 (maintenance) as well as two producing departments P1(forming) and P2 (finishing). S1 allocates costs based on engineering hours, S2 allocates costs on the basis of human resources hours, and S3 allocates costs based on maintenance hours.

When determining which of these would be allocated first, do I look at total hours and code the one using the fewest? The text says you allocate cost first to the department that finishes first.