Ortho-phenanthroline reacts with ferrous ion to produce a deeply colored complex with a molar absorptivity (s) of 11,100 L/mol1 cm-1 at a max of 508 nm. You diluted the stock colored complex that you were provided using a 4 fold serial dilution. You measured the third dilution in the series in a plastic cuvette with a pathlength of 0.5 cm at 508 nm and obtained an absorbance of 0.73482. What was the concentration of the original stock solution in mM?