Can you help to derive a formula that can calculate b2, b3, b4 where
T = a1(b1) + a2(b2) + a3(b3) + a4(b4)
b1 = x1
T = y
For example, one solution is b1=16%, b2=26%, b3=46% for
Y = 2 and x1=12%
2 = 0.25(12%) + 0.25(16%) + 0.25(26%) +...