A sample of methylcyclohexane is suspected of being contaminated with toluene, from which it had been prepared by hydrogenation. At 261 nm, toluene has a molar absorptivity ϵ = 224, whereas methylcyclohexane does not absorb at that wavelength (ϵ = 0). An ultraviolet spectrum of the contaminated methylcyclohexane (obtained in a 1.0 cm cell) shows an absorbance A 5 0.65 at 261 nm. Calculate the concentration of toluene in the methylcyclohexane.