Given the molar absorptivity for a species X of 1600 M-1cm-1 at a wavelength of 270 nm, and 400 M-1cm-1 at a wavelength of 540 nm. For species Y, the molar absorptivity at 270 nm is 200 M-1cm-1 and 8000 M-1cm-1 at 540 nm. For a certain mixture, the absorbance at 270 nm is 0.5 and, at 540 nm, is also 0.5. What is the concentration of species Y in the mixture