Man, I think I have figured out a bit more of what you posted:
Step 4 means that @ t-x, A1=100, A2=100, B1=100, B3=100
If at t-(x+1) A1=15, A2=25; B1=51.2, B2=13
Then when normalized at t-(x+1) A1=100.50 or 100.03?
I would guess the latter, but am thinking there might be yet a better way.