An unknown substance has a concentration (C) of 1.23 mg/ml and has an absorbance (A) of 0.384 at 493 nm. Given that the path length for the spectrophotometer (1) is equal to 1.00 cm, what is the extinction coefficient (E) for the substance at 493 nm. 3.20 mg-cm/mi O 0.312 ml/mg-cm O 0.472 ml/mg.com O 0.312 mg-cm/ml