ΔT=1-(a1/a2)•ln(t+1)
(a1/a2)•ln(t+1) = 1 - ΔT
ln(t+1) = (1 - ΔT)•(a2/a1)
t+1 = e^( (1 - ΔT)•(a2/a1))
t = e^( (1 - ΔT)•(a2/a1)) - 1
b•(1-ln(a/t))=r1/r2
1-ln(a/t)=r1/(r2•b)
1-ln(a) + ln(t)=r1/(r2•b)
ln(t)=r1/(r2•b)-1 + ln(a)
t = e^(r1/(r2•b)-1 + ln(a) ) = e^(r1/(r2•b)) • a/e