Management Model: Single-Period Model 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 $5.00 a box. The lettuce is sold for $15.00 a box and the dealer that sells old lettuce is willing to pay $1.60 a box. Past history says that tomorrow's demand for lettuce averages 240 boxes with a standard deviation of 36 boxes. How many boxes of lettuce should the supermarket purchase tomorrow ______? (Use Excel's NORM.S.INV function to find the z value. Round your answer to the nearest whole number. Enter the numbers only)