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

### Instruction:
 苏和她的姐姐买了一辆价值2100美元的车。她们同意按照使用天数的百分比来分摊费用。苏的姐姐每周开车4天，苏将获得其余的天数。苏需要支付多少钱？


### Response:
 苏每周开车3天。
所以她需要支付2100*3/7=900美元。