The manager of a car wash uses 5,500 gallons of soap each year and operates the car wash 360 days a year. Ordering costs are $28 and carrying costs are $2 per gallon. If the manager buys under 500 gallons at a time, the price is $1.80. 500-899 gallons cost $1.60 and more than 900 gallons ordered at one time is $1.52. What is the optimal order quantity? PLEASE SHOW WORK