<s>[INST] When shopping at a grocery store, you can often find sales where items are "buy one, get one free" (B1G1). Most people put the free item in their cart as if it is actually free in the end. However, the issue is that the store doesn't always put a price sticker on the free item. If the items have multiple prices (due to different quantities or flavors), it's potentially not clear which price is used for the free item. In your experience or research, how do you determine the first item's price and the value of the B1G1 deal, especially when there are multiple prices?[/INST]