Fts 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, fts printed 20 copies of the books based on the client’s estimate of the number of people who would attend the course. each workbook costs $30 and is sold to course participants for $50. this cost includes a royalty fee paid to the author and the cost of duplication. calculate the workbook cost in total and per student, assuming that 18, 20, or 22 students attempt to attend the course. classify the cost of workbooks as fixed or variable relative to the number of students attending the course.