Determine the keq for the formation of fescn2

Question

The hydrazine reduces CrO₄^2- to Cr (OH)₄^- in base (hydrazine is oxidized toN₂).

solution        absorbance      [Fe³⁺]    [SCN^-]
unknown 1       0.158          1.0x10^-3     2.0x10^-4
unknown 2      0.308          1.0x10^-3 4.0x10^-4
unknown 3      0.457      1.0x10^-3    6.0x10^-4
unknown 4      0.609          1.0x10^-3    8.0x10^-4
unknown 5      0.743         1.0x10^-3     1.0x10^-3

a. By using the Use ICE table, determine the equilibrium concentrations of  SCN^- and Fe³⁺.

b. By using the equilibrium concentrations, determine the Keq for the formation of FeSCN²⁺ 

c. How to compare it to Keq literature value, and determine for their % difference?