EPM functions

Hello experts, Guide me TO knowledge base on "EPM Funtions".

also

I have 5 years of historical data of exchange rates in RATE MODEL. I would like to take average of all the December rates and would like to post the same value to next year plan data. How to achieve this logic in sap bpc 10.0 nw. script logic would be good or EPM functions?

Thank you in advance