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

### Instruction:
 Nicky anabadilishana kadi za mpira wa kikapu na Jill. Ikiwa Nicky anabadilisha kadi mbili zenye thamani ya $8 kila moja kwa kadi moja yenye thamani ya $21, anapata faida ya kiasi gani?


### Response:
 Kwanza, ongeza gharama ya kadi mbili za $8: $8 + $8 = $<<8+8=16>>16
Kisha toa gharama ya kadi ambazo Nicky ametoa kutoka kwa gharama ya kadi aliyopokea ili kupata faida yake: $21 - $16 = $<<21-16=5>>5