阅读理解
Sam: Excuse me!
A man: Yes?
Sam: Where is the library?
A man: It is far from here.
Sam: How can I get there?
A man: You can get there by bus.
Sam: But where is the bus stop?
A man: Cross the street, it's over there.
Sam: Thank you.
A man: My pleasure.
的准线与圆(
相切,则P的值为( )