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

### Instruction:
 Mark anataka kumpa mtoa huduma yake asilimia 20 kwenye bili ya $200. Ikiwa rafiki yake anakubali kuchangia $10, Mark anapaswa kuongeza kiasi gani?


### Response:
 Kwanza tafuta jumla ya kiasi cha mshahara: 20% * $200 = $<<20*.01*200=40>>40
Kisha toa mchango wa rafiki: $40 - $10 = $<<40-10=30>>30