【求助】Linux 的指令...

I have to accomplish the following tasks:

(a) A listing of all the files under the /etc directory and its sub-directories that have been created or changed since the system was booted.
(b) A listing of all the files under the /dev directory and all its sub-directories that have been created or modified in the last 30 minutes.
(c) A listing of all the files under the /home directory and all its sub-directories that have been created or modified within the last 7 days.
(d) A listing of all the files under the /tmp directory and all its sub-directories that were more than 30 days old.

i need to use the command to do this.. i know need to use "find" command, i am quite confuse about that. Can anyone help me.??
:(

Let me try...

(b) find /dev -cmin -30 -o -mmin -30

(c) find /home -ctime -7 -o -mtime -7

(d) find /tmp -ctime +30

i got it.. thanks a lot..~~~