4. The actual molar extinction coefficient for o-nitrophenol has been calculated and used to develop a simple formula for calculating -galactosidase activity. This formula is Activity Units = A420 X 0.380/minutes at 37 C where one unit of activity is the amount of enzyme needed to convert 1 Mu mole of ONPG to o-NP in one minute. Suppose a preparation of beta -galactosidase was made in the laboratory. One Mul of this preparation was added to 99 Mul of buffer. 10 Mul of this solution was then added to 1.0 ml of reaction buffer and equilibrated to 37 C. 0.2 ml of ONPG was added and after 11 minutes. the reaction was stopped by added 0.5 ml of sodium carbonate. The absorbance of the solution was then found to be 0.412. What was the enzyme activity in the original solution ?n units/ml?.