Skinner's fish market buys fresh boston cluefish daily for $4.20 per pound and sells it for $5.70 per pound. At the end of each business day, any remaining bluefish is sold to a producer of cat food for $2.40 per pound. Daily demand can be approximated by a normal distribution with the mean of 180 pounds and a standard deviation of 50 pounds. What is the optimal order quantity?