[The following information applies to the questions displayed below.]

Thornton Training Services (TST) provides instruction on the use of computer software for the employees of its corporate clients. It offers courses in the clients offices on the clients equipment. The only major expense TST incurs is instructor salaries; it pays instructors $5,200 per course taught. TST recently agreed to offer a course of instruction to the employees of Novak Incorporated at a price of $440 per student. Novak estimated that 20 students would attend the course.

Base your answers on the preceding information.

TST sells a workbook with printed material unique to each course to each student who attends the course. Any workbooks that are not sold must be destroyed. Prior to the first class, TST printed 20 copies of the books based on the clients estimate of the number of people who would attend the course. Each workbook costs $31 and is sold to course participants for $43. This cost includes a royalty fee paid to the author and the cost of duplication.

11. Calculate the workbook cost in total and per student, assuming that 18, 20, or 22 students attempt to attend the course.

12. Classify the cost of workbooks as fixed or variable relative to the number of students attending the course.