I recall there was an old thread here regarding how the
L1R5/L1R4 is computed.
This is the updated information I got from the JAE Booklet 2010 and
the SEAB Hotline.
Hope this helps those of us taking O' Levels this year.
As for the L1R2B2 computation, I didn't ask as I don't plan on
going to a polytechnic.
L1R2B2 for poly is simply english, maths and science/humans
depending on whether you want a science or arts base diploma course
and 2 other subjects.