"What's the problem with using 255.255.255.247 as a subnet mask if you want to make a LAN subnet with 12 hosts?" (5 word answer)
Unemployment Office Is That Way -> Is the only 5 word answer I could come up with. The correct answer "invalid netmask", is only two words.
"What TCP destination port numbers should be allowed through the perimeter stateful firewall device to and from a mail server whose only purpose is to proxy SMTP mail from internal sources?" (one number answer)
Short Answer: There is no answer to the question that can be expressed in one number. Outbound connections to TCP destination port 25 only. Returning traffic (including associated ICMP) should be automatically handled by your stateful inspection firewall. If not, you need to buy a better firewall. Any applicant who provides any answer should the rejected out of hand as (a) being unable to read (b) being a threat to security. Unless, of course, you have misphrased the question. --- () ascii ribbon campaign against html e-mail /\ www.asciiribbon.org