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

### Instruction:
Tommy wants to earn enough money to buy 8 new books. Each book costs $5. If Tommy already has $13, how much does he need to save up?

### Response:
 Vitabu vitagharimu $40 kwa sababu 8 x 5 = <<8*5=40>>40
Anahitaji kuokoa $27 kwa sababu 40 - 13 = <<27=27>>27