1. A retired couple supplement their income by making fruit pies, which they sale to a local grocery store. During the month of September, they produce apple and grape pies. The apple pies are sold for $5.50 to the grocer, and grape pies are sold for $5.20. The couple is able to sell all of the pies they produce. They use flour and sugar which purchase monthly. For the month of September, they have 1800 cup of sugar and 2100 cups of flour. Each apple pie requires 2 cups of sugar and 3 cups of flour, and each grape pie requires 3 cups of sugar and 3 cups of flour. The couple want to work no more than 60 hours making pies. Each apple pie takes 6 minutes, and each grape pie takes 3 minutes to make.

a. Determine the number of grape and apple pies that will maximize the revenues.

b. Determine the amounts of sugar, flour, and time that will be unused.