changing the httpd header and limiting the total amount of data

[Hamza Eraldi]

I am using FreeBSD 5.3 with apache 1.3.33..
Could you please write that how can i change the apache's header? 
example:
from 
Apache/1.3.31 (Unix) PHP/4.3.6 anothermodule/version....etc
to
'Webserver', or 'unknown', or something like that..
And my second question is:
How to limit the total amount of transfered data of virtualhosts?
(Like xxx.com : 10 GB/month, yyy.com: 15 GB/month, zzz.com: 30 GB/month)
Thanks in advance..
Best regards.

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