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

### Instruction:
John decides to get the vaccine for COVID.  He has to wait 20 minutes for the first dose.  The second dose has a wait time half as long.  How long was the total wait time?

### Response:
 เข็มที่สองต้องรอเวลา 20/2 = <<20/2=10>>10 นาที
ดังนั้นเวลารอทั้งหมดคือ 20+10 = <<20+10=30>>30 นาที