# Finding the wavelength of maximum absorption of Tartrazine using Fieser-Kuhn

How would you use Fieser-Kuhn rules to calculate the wavelength of maximum absorption for tartrazine?

Fieser-Kuhn rules states that: $\lambda_{max}=114+5M+n(48-1.7n)-16.5\ R_{endo} - 10\ R_{exo}$

1. What would $M$ be in this example? There aren't any alkyl substituents, but what I'm not sure about ring residues. Would this refer to the $SO_3Na$ and $COONa$?

2. Would $n$, the number of conjugated double bonds be equal to 12?

1. Does Pyrazole count as a ring for $R_{endo}$? So $R_{endo}=3$?

Or would Woodward-Fieser rules be more suitable to use in this scenario?