a                     b               c
-0.591837590400355 2.0653899667818 -0.11690

B-log(B)=sb

1<sb<5;  B= f(sb); f(x) = a + b*x + c*x**2

a                      b              c
1.15480408924031 1.18368915071855 -0.00462208
5<sb<15;   |error|  mostly 0.1% max 0.3%


1.93681624696356 1.07493142883256 -0.0007441876
15<sb<35;  
   |error| < 0.02 % max 0.05 %

