3. In the infrared spectra of styrene/acrylonitrile copolymers, the ratio of the absorbances of the CN nitrile stretching vibration at 2250cm1 and the polystyrene aromatic ring-stretching vibration at 1600 cm-1 may be employed as a measure of the composition. Infrared analysis of a number of styrene/acrylonitrile copolymers of known compositions yielded the results listed in Table 1 below. The infrared spectrum of a sample of poly(styrene-co-acrylonitrile) of unknown composition was recorded. The absorbance values at 2250 and 1600cml in this spectrum were 0.42 and 0.15, respectively. Estimate the composition of this sample Cable 1. Infrared analysis data obtained for a number of styrene/acrylonitrile copolymers