补全对话。
—____ are we going to do this summer?
— Let's go to Sanya.
—____ do we go there?
— We get there by plane.
将函数 f(x)=3sinx-11cosx2001的图象向右平移a(a>0)个单位,所得图象的函数为偶函数,则a的最小值为 ( )