Hi,
Often, we were asked about this question. And we get different answer on it. Some says 70 point, others say it should be 120 point. And I even cannot found any clue in FMEA Manual.
When I searched in the Automotive forums for RPN I got 37 hits.
I am not trying not to answer but I think that it is better for you to do some research here and see what others have said.
Self help is the best form of help.