Rachel paid $600 per month to rent a workshop. She paid weekly salaries to her three employees, amounting to a total of $3600 for a month. She also purchased insurance coverage for her workshop (and her business) at a monthly premium of $300. She then spent $1,200 on purchasing raw materials each month. What was the average total cost of her establishment if she sold 300 units every month? Rachel’s average total cost is _? per month.