The first is b, the second is a and the third is b
It will be 2.8 inches long
2(books)*$3.50=$7.00
4(books)*$5.25=$21.00
Total bill=$34.00
$34.00-($7.00+$21.00)=$6.00
The 3 books was sold for $6.00 but its original selling price is $6.00*2 which is $12.00 reason being the books was sold for half the original price.