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

### Instruction:
A store marks a book 30% above the cost. But during a sale, a 10% discount was given. If the book costs $50, what is the percent profit?

### Response:
 Pato la ziada lilikuwa 30% ya gharama.
Punguzo lilikuwa 10% ya gharama.
Faida ilikuwa 30% - 10% = <<30%-10%=20%>>20% ya gharama.