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

### Instruction:
You can lower the price by 20% if you buy more than fifteen units of iPhone cases. If you pay $500 to buy 18 units, what is the original price?

### Response:
 Ikiwa unanunua vitengo 18, asilimia ya bei jumla inapungua hadi 100% - 20% = 80%
Ikiwa 80% ni sawa na $500, basi 100% ni sawa na 100%/80% * $500 = $625