You are at a department store looking for items to buy for your home office. As you're browsing, you notice none of the items are directly priced. You notice three signs comparing prices in an odd way: (1) Buy 16 Pencil Boxes and 8 Lamps for the price of 7 Office Chairs (2) Buy 11 Lamps and 7 Office Chairs for the price of 9 Pencil Boxes (3) Buy 3 Office Chairs and 9 Pencil Boxes for the price of 8 Lamps You watch another customer go up to the checkout with one Office Chair and one Pencil Box, and you heard that the pencil box was $42 less than the Office Chair. Once the checkout was complete, the cashier noticed that one of the signs listed above was incorrect. Which sign is incorrect, and how much does a Lamp cost?