Below is an instruction that describes a task. Write a response that appropriately completes the request in English. Please answer in English.

### Instruction:
Sally teaches elementary school and is given $320 to spend on books for her students. A reading book costs $12 and there are 30 students in her class. Unfortunately, if the money she is given by the school to pay for books is not sufficient, she will need to pay the rest out of pocket. How much money does Sally need to pay out of pocket, to buy every student a reading book?

### Response:
To purchase a book for each student, Sally needs: 30 x $12 = $<<30*12=360>>360.
You can find the difference between what Sally needs and what she has by subtracting $360 from $320: $360 - $320 = $<<360-320=40>>40.
#### 40