A tank of water was contaminated with a colored dye (D). To determine the concentration of D, an analyst took 5.0-mL solution from the contaminated water as a sample, and measured the absorbance, yielding a value of 0.10. Afterwards, the analyst added 5.0-mL of 0.02 M standard D solution into the sample solution, and measured the absorbance, yielding a value of 0.20. What is the concentration of D in the original sample solution