某校准备组织290名学生进行野外考察活动，行李共有100件。学校计划租用甲、乙两种型号的汽车共8辆，经了解，甲种汽车每辆最多能载40人和10件行李，乙种汽车每辆最多能载30人和20件行李。
（1）设租用甲种汽车x辆，请你帮助学校设计所有可能的租车方案；
（2）如果甲、乙两种汽车每辆的租车费用分别为2000元和1800元，请你选择最省钱的一种租车方案。
解：（1）设租用甲种汽车x辆，则租用乙种汽车（8-x）辆。
依题意得：
解得
方案①：当
时，
方案②：当
时，
即：租用甲种汽车5辆，乙种汽车3辆或者租用甲种汽车6辆，乙种汽车2辆
（2）设总费用为W元，则
∵200>0 ∴W随着x的增大而增大。
∴x=5时，W最小值为15400元。
| 阅读理解。 |
| There are four people in the twins' family. They are the twins, their mother and their father. The twins' names are Lucy and Lily. They are fourteen. They are in the same class in No. 3 Middle School and they are all good students. Their father Mr. King is a teacher. He's thirty-nine. He teaches English in a school near his home. Their mother, Mrs. King is a doctor. She works in a hospital. Now, they are all at home. They are very happy. |
| 1. There are ______ people in the twins' family. |
[ ] |
| A. three B. four C. five D. six |
| 2. Mr. King is a ______. |
[ ] |
| A. worker B. teacher C. doctor D. student |
| 3. Mrs. King works ______. |
[ ] |
| A. in a school B. in a factory C. in a hospital D. at home |
| 4. How old is Mrs. King? |
[ ] |
| A. Thirty. B. Thirty-nine. C. Thirty-two. D. We don't know. |
| 5. The twins are in ______ Middle School. |
[ ] |
| A. number one B. number two C. number three D. number four |