Problem $20-4($Algo$)$

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 $$3\mathrm{.}00$ a box. The lettuce is sold for $$14\mathrm{.}00$ a box and the dealer that sells old lettuce is willing to pay $$1\mathrm{.}50$ a box. Past history says that tomorrow's demand for lettuce averages $235$ boxes with a standard deviation of $35$ boxes.

How many boxes of lettuce should the supermarket purchase tomorrow? $($Use Excel's NORMSINV$)$ function to find the correct critical value for the given $a-$level. Do not round intermediate calculations. Round your answer to the nearest whole number.$)$

Number of boxes