求英语高手看下这一小段话.M:I can't find my textbook for Biology 101.W:I'

求英语高手看下这一小段话.
M:I can't find my textbook for Biology 101.
W:I'm sorry,but we're sold out.
M:Sold out!How can that be?
W:We received the wrong number of books.We are fifty boiks short.
M:But what am I going to do?I had my first class this morning and already we've been assigned two units to read for Friday.
W:We'll be getting the books next Monday.
M:But that doesn't help me now!
W:Why not ask someone who has a book to share it with you?
M:I live off campus and don't know anyone in my class yet.
W:Come to think of it,my roommate is taking biology,and I know she bought her books yesterday.I'll ask her if she'll let you borrow it for a day to get your reading done.
M:Oh,that would be great.
首先,男的说找不到他的课本,但是为什么女的说书本卖完了?而且We‘re sold out.不是变成了“我们被卖完”?下句接着还说搞错了书的数目,还缺了50多本.还有下周五我们去拿书.这些和那个男的丢书有何关系?还有"my roommate is taking biology"是我的室友在上生物课的意思吗?
ww·mm·ww “We're sold out的意思是说：你要的书卖完了 ”既然是这么翻译，那为什么这句话要用被动，而不用主动？用被动，“we”变成是“sold out”的对象了啊。
菜鸟等大虾 books是我打错了……但是那句We've sold out.确实书本这么写……