A 5.0 mL aliquot of a stock tryptophan solution was diluted by adding up 95 mL of water. The absorbance of that diluted solution was measured at 280 nm as 0.055 absorbance units. Determine the concentration of the stock (original) solution?
Hint: Make sure to compute the dilution factor. (Molar extinction coefficient = 5579 cm-1 M-1.)