I want to use a function to determine how many bonus tickets I should give
out at the end of each month. One (1) ticket for every three (3) apples sold
and the number of bonus tickets are culmulative.
For example, here is a table:


Date ApplesSold #BonusTicket RepName
jan 2 0 JOHN
feb 3 1 JOHN
mar 7 3 JOHN
apr 5 4 JOHN
may 12 8 JOHN
jun 14 12 JOHN
jul 19 18 JOHN
aug 21 25 JOHN
sep 1 25 JOHN