The local supermarket buys lettuce each day to ensure really fresh produce. Each morning, any lettuce that is left from the previous day is sold to a dealer that resells it to farmers who use it to feed their animals. This week, the supermarket can buy fresh lettuce for $6.00 a box. The lettuce is sold for $18.00 a box and the dealer that sells old lettuce is willing to pay $3.60 a box. Past history says that tomorrow's demand for lettuce averages 254 boxes with a standard deviation of 37 boxes. How many boxes of lettuce should the supermarket purchase tomorrow