Absorbance reading of unknown solution containing caffeine is 0.376. A spiked is prepared by adding 25.0 mL of 200.0 ppm caffeine standard solution to a 100.00 mL volumetric flask, then diluted to the mark with the unknown solution. Absorbance reading for this spiked solution is 0.589.

A. What is the final concentration of added caffeine standard?

B. Using the standard addition formula determine the amount of caffeine in the unknown.