A small grocery store sells fresh organic salad, which it obtains from a local farmer. The grocery store buys fresh salad weekly for exist4.20 per pound and sells for exist8.70 per pound. At the end of the week, any remaining salad is sold to a producer for exist1.40 per pound. Weekly demand can be approximated by a normal distribution with a mean of 80 pounds and a standard deviation of 12 pounds. What is the optimal stocking level?