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

### Instruction:
A milk teas shop was able to sell a total of 50 cups of milk tea yesterday. Two-fifths of their sales are winter melon flavor, three-tenths are Okinawa flavor, and the rest are chocolate flavor. How many cups of chocolate-flavored milk tea were they able to sell yesterday?

### Response:
 Duka la chai ya maziwa liliuza vikombe 50 x 2/5 = <<50*2/5=20>>20 vya chai ya maziwa yenye ladha ya melon ya majira ya baridi.
Waliuza vikombe 50 x 3/10 = <<50*3/10=15>>15 vya chai ya maziwa yenye ladha ya Okinawa.
Hivyo walikuwa wameuza jumla ya vikombe 50 - 20 - 15 = <<50-20-15=15>>15 vya chai ya maziwa yenye ladha ya chokoleti.