The Piedmont School of Music has hired you as a consultant to help in analyzing the behavior of the school's costs. Use the account-classification method of cost estimation to classify each of the following costs as variable, fixed, or semivariable. Before classifying the costs, choose an appropriate measure for the school's activity.

Wages of the school's part-time assistant recital instructors. These employees are hired on a temporary basis. For each student enrolled in the school's music programs, four hours of assistant instructor time are needed per week.