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

### Instruction:
John starts at an elevation of 400 feet.  He travels downward at a rate of 10 feet down per minute for 5 minutes.  What is his elevation now?

### Response:
 เขาเดินลงไปทั้งหมด 10 x 5 = <<10*5=50>>50 ฟุต
ดังนั้น เขาอยู่ความสูง 400 - 50 = <<400-50=350>>350 ฟุต.