The local supermarket buys lettuce each day to ensure really fresh produce. The supermarket buys fresh lettuce for $4.75 per box and sells it for $7.50 per box. 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. The resellers pay $2.00 per box and the supermarket spends an additional $0.75 per box to get the lettuce repackaged to sell to the reseller. Past history shows that tomorrow's demand for lettuce averages 250 boxes with a standard deviation of 34 boxes.
a) What is the target service​ level? Enter your response as a percentage rounded to nearest whole percentage (xx%).
b) How many boxes of lettuce should the supermarket purchase? Round to nearest whole number.