Concurrent Managers

Hi,

I am a System Administrator for Oracle EBS R12 and I missed the Feb. 9 Seminar on this topic. I have few questions on the topic, please advise; 

1. Is there a limit on cache size? For example, if I am running 45 processes under Standard Manager, is it ok for Cache size to be 90?
2. I have set our Standard Manager to 45 processes, due to the number of concurrent requests we have running in the application. Is this normal?
3. How do I assess server capacity? And how do I know a specific capacity is capable for X number of processes?

Thanks,

Douter.