How are Absorbance and Extinction Coefficient computed?

Extinction Coefficient

Extinct(Prot) = (Tyr count)*Ext(Tyr) + (Trp count)*Ext(Trp) + (Cys count)*Ext(Cys) where Ext(Tyr) = 1490, Ext(Trp) = 5500, Ext(Cys) = 125

Absorbance

Absorb(Prot) = Extinct(Prot) / Molecular_Weight

There is a boolean parameter to be set - assumeCysReduced.
If assumeCysReduced is set to true, (Cys count) will always be 0.
If assumeCysReduced is set to false, Every pair of Cystine will be counted as 1.
Our approach is based on here.