141. Solving a chemistry problem

The content of normal butane and isobutane in a mixture with indifferent impurities was determined by the absorption bands at 10.3 μm (absorbs only n-butane) and at 8.5 μm (absorbs only isobutane). The following data were obtained for standard mixtures:
Absorption at 10.3 μm,% 18.0 28.5 39.0 49.0 54.0
W (n-butane),% 18.0 36.0 58.0 79.0 92.0
Absorption at 8.5 μm,% 22.5 41.0 53.0 63.0 69.0
W (isobutane),% 15.0 42.0 61.0 83.0 95.0
Calculate the mass fraction (%) of n-butane and isobutane in the mixture if the following results are obtained for them under the same conditions:
Option 1
Absorption at 10.3 μm,% 20.0
Absorption at 8.5 μm% 60.0