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

### 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:
 ร้านชานมขายได้ 50 x 2/5 = <<50*2/5=20>>20 แก้วของรสเมล่อนหนาว
ร้านขายได้ 50 x 3/10 = <<50*3/10=15>>15 แก้วของรสโอกินาว่า
ดังนั้น ร้านขายได้ทั้งหมด 50 - 20 - 15 = <<50-20-15=15>>15 แก้วของรสช็อกโกแลต