The Stick-em-Quick Inoculations Center provides early childhood checkups and vaccinations for children in the South Bronx. It pays annual rent of $ 25,000 and has a permanent staff consisting of a nurse practitioner and an administrative assistant, who are paid $ 125,000 per year. The Center hires doctors on a per-diem basis to provide exams and uses $ 15.00 worth of supplies for each exam not including vaccines. Inoculation appointments are scheduled in advance and the Center needs one per-diem doctor for every 100 children they have scheduled on any given day. It also spends $ 7.50 per child for the vaccines used in its inoculations program. Which of Stick-em’s expenses are?
a. Fixed
b. Step-fixed or semi-variable costs
c. Variable