Who is asked to call back? Why does the man want the women to find someone to cover Tom?

M: Peterson and Taylor. Can I help you?
F: Yes, this is Isabel Hawkins from R & D. Can I speak to Dorothy Borrow, please?
M: I am afraid she is out at the moment. I am the secretary, Francis Gregory. Can I take a message?
F: Yeah, ask her to call me back this afternoon.  My number is 345 -517 -7563. Thank you.
M: You are welcome.

M: Mary, can you find someone to cover Tom? He is sick at home.
F: OK. Can I find a girl to do Tom’s job?
M: Certainly, but you’d better get a male clerk to do Tom’s job.
F: I see. When can Tom come back to work?
M: I am not sure. Perhaps in a week or so.