two servers

Hi
I have two servers, both with an individual broadband line to
connect the outside world, and they are connected each other through
an intranet too. If the apache in server A proxypass a http request to
server B. How is the server B response to the request? it will
response through server A (server B -> server A -> server A's
broadband line -> user), or it will response to the user by using its
own broadband line (server B -> server B's broadband line -> user)?

thanks
from Peter (cmk128@hotmail.com)