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

### Instruction:
 约翰每天写20页。他要写3本每本有400页的书需要多长时间？


### Response:
 他想要写3*400=<<3*400=1200>>1200页。
所以他需要1200/20=<<1200/20=60>>60天。