need answer!

Conceptual questions: a) What does packet filtering firewall examine in a packet? b) What does stateless firewall mean? c) Does packet filter examine the payload of a packet? d) A company has perimeter-based firewall and they authorized port # 80, because they want to tell the world about the company but the company administrator wasn't aware that they were using old version of webserver which has a Buffer Overflow bug. Can the firewall protect a hacker from the internet to exploit this bug? Application questions: a) Write a rule to allow inbound mail (SMTP, port25) but only to our email server with IP address 192.168.0.25. b) Write a rule to block all traffic from IP address ranges from 123.45.67.1 to 123.45.67.255.