You have tested one good and one bad colorimeters with a colored solution at two path lengths of light and recorded transmittance that is fraction of incident light that passed through the colored solution. According to Beer-Lambert Law transmittance should drop exponentially with path length. Input A has two transmittances for one colorimeter. Input B has two transmittances for the other colorimeter. Input C has two path lengths correspondingly. Output 'A' if first colorimeter is good, output 'B' if second colorimeter is good.