某公司市场营销部的某营销员的个人月收入与该营销员每月的销售量成一次函数关系，其图象如图所示，根据图象提供的信息，解答下列问题：

（1）求营销员的个人月收入y元与该营销员每月的销售量x万件（x≥0）之间的函数关系式；

（2）若两个月内该营销员的销售量从2万件猛增到5万件，月收入两个月大幅度增长，且连续两个月的月收入的增长率是相同的，试求这个增长率（保留到百分位）．

    It's Sunday. Children don't go to school on Sundays. But Kate gets up early in the morning. “It's my birthday. I'm eight years old today.” she thinks, “Where are Dad and Mum? I want to know what they can give me for my birthday.”

    Her father and mother are not at home. They are going shopping. And now they are talking about what to buy for Kate.

—Dad: How about the doll? It looks nice. I think Kate would like the doll.

—Mom: I don't think so. She is not a little girl. I think she likes a new dress. Girls often like new dresses very much.

—Dad: But she has a few new dresses and some new blouses. Oh, I think she must be very happy to have a box of colorful pencils and some picture books. Do you think so?

— Mom: Yes. Let's go over there and buy them.

如图，在研究光的反射定律实验中，