A DNA extract solution with a concentration of 15 ng/µL placed in a micro-cuvette of sample thickness 0.5 mm gave an absorbance of 0.24 at a wavelength of 260 nm in a spectrophotometer. After further concentration, the sample was found to give an absorbance of 0.38 at the same wavelength under identical conditions. The final concentration of the sample is _________ ng/µL. (Give your answer rounded off to 2 decimal places.)