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

### Instruction:
 Bob ananunua dawa ya pua. Ananunua 10 kwa ajili ya ofa ya "nunua moja pata moja bure". Kila moja inagharimu $3. Anapaswa kulipa kiasi gani?


### Response:
 Bob ananunua dawa ya pua 10. Anapata 5 bure. Hivyo analipa tu kwa 5. 5*3 = <<5*3=15>>15 dola.