题目

Dear Editor,  My name is Greg and I am a reader of your maganine.I would like to tell you something about my friends.I came to study at a new school here two years ago. I found it more difficult to make friends here than at my old school.However,I still made two new friends.One of them is Jenny.She is the first person I met in my new class and she is very kind to me.She is a good listener and she can always keep my secrets.I have not met many people like Jenny at my new school,and I think Jenny is a very special girl.I like her very much. I met James,my other best friend,at an ice-skat已知函数f（x）=|x-3|+|x-4|．（Ⅰ）求不等式f（x）≥2的解集；（Ⅱ）如果f（x）≤a的解集不是空集，求实数a的取值范围．