听力原文：M: What's that book you just picked up? W: The sociology text professor Smith uses in his course. M: You had better read it if you want to pass the course. W: But it is too expensive. I simply can't afford it. M: How much does it cost? W: It costs 40 dollars. M: Did you check the used book section here? Maybe they have one. W: No, they don't. I have asked. M: Why don't you get it from the library? W: Are you joking? I've been trying for months and the book is always out. There are more than 45 students in the course and every single one wants the book. M: Listen, you know my roommate, Henry, don't yon? He took the same course last year and I believe he owns the book. I'll ask him if he'll lend it to you. W: Oh, Tom, that would settle everything. That's very kind of you. M: My pleasure. Why doesn't the woman buy the book?