Alana wants to buy 4 books. There are 4 shops that sell the books that she wants. The shops, the prices of the books and any special offers are shown in the following table:
| standard price of a book | special offer | |
| shop A | $24 | buy 2, get a 3rd one for half price |
| shop B | $20 | none |
| shop C | $26 | buy 3, get a 4th one free |
| shop D | $25 | buy 1, get a second one for half price |
Alana wants to buy all her books from the same shop and to spend as little as possible.