阅读短文，回答下面的问题。

    Mary, Jane and May are very good friends. Mary is shorter than May. May is heavier than Jane. Jane is thinner than Mary. How old are they? Mary is 7 years old. Jane is 12 years old. And May is two years older than Jane. They study at Qinglan Primary School. Mary likes English, Jane likes maths and May likes music. They all study hard.