Williams Performance Company manufactures sports cars. After making a sale, the salesperson sends the car to be detailed before the customer takes it home. Detailing the car takes 30 minutes at a cost of $18 per hour for direct labor and $4 per car for materials. If the average salesperson sells four cars per day, what is the average cost per 5-day week for detailing cars? (Do not round intermediate calculations. Round your final answer to 2 decimal places.)