First introduced in Los Angeles, the concept of Korean style tacos sold from a catering truck has been gaining popularity nationally (The New York Times, July 27, 2010). This taco is an interesting mix of corn tortillas with Korean-style beef, garnished with onion, cilantro and a hash of chili-soy dressed lettuce. Suppose one such taco truck operates in the Detroit area. The owners have estimated that the daily consumption of beef is normally distributed with a mean of 24 pounds and a standard deviation of 6 pounds. While purchasing too much beef results in wastage, purchasing too little can disappoint customers.

a. Determine the amount of beef the owners should buy so that it meets demand on 80 percent of the days.

b. How much should the owners buy if they want to meet demand on 95 percent of the days?