Puzzle #24 wasn't thought up by us, but rather by the young daughter of a friend of mine. Her mother had gone to the grocery store, and upon coming home, her daughter had sorted their groceries into two piles. She took a picture of them and asked her friends if they could figure out the rule that had been used to sort the items. I've recreated it here.
Items are in three groups. The first two groups have been sorted according to the rule. Your task is to pick items in the third group that belong in the second group. Make a note of the letters next to those items, and group them together in alphabetical order. That group of letters is a 15% discount code.