Shopping is not as simple as you may think! There are all sorts of tricks at play each time we reach out for that particular brand  of product on the shelf. Colouring, for example, varies according to what the producers are trying to sell. Health foods are packaged  in greens, yellows or browns because we think of these as healthy colours. Ice cream packets are often blue and expensive goods, like chocolates, are gold or silver. When some kind of pain killer was brought out recently, researchers found that _ because they made the product look weak and ineffective. Eventually, it came on the market in a dark blue and white package--blue because we think of it as safe, and white as calm. The size of a product can attract a shopper. But quite often a bottle doesn't contain as much as it appears to. It is believed that the better-known companies spend, on average, 70 percent of the total cost of the product itself on packaging! The most successful producers know that it's not enough to have a good product. The founder of Pears soap, who for 25 years has used pretty little girls to promote   their goods, came to the conclusion: "Any fool can make soap, but it takes a genius  to sell it." Which of the following may trick a shopper into buying a product according to the text?
The cost of its package. The price of the product. The colour of its package. The brand name of the product.