To determine the concentration of iron in the sample using Beer's law, we first need to know the relationship between absorbance and concentration for iron. Beer's law is given by the equation:A = * b * cWhere:A = absorbance = molar absorptivity L/molcm b = path length cm c = concentration mol/L We need a calibration curve to find the value of for iron. A calibration curve is a plot of absorbance versus concentration for a series of standard solutions with known concentrations. From the calibration curve, we can determine the slope, which is equal to * b.Once we have the slope, we can use the absorbance values from the unknown sample to determine the concentration of iron. Since we have three absorbance values 0.3, 0.6, and 0.9 , we can calculate the average absorbance and use that value in our calculations.Average absorbance = 0.3 + 0.6 + 0.9 / 3 = 0.6Now, we can rearrange Beer's law equation to solve for the concentration:c = A / * b Assuming we have the slope from the calibration curve, we can plug in the average absorbance and solve for the concentration:c = 0.6 / slope Without the calibration curve and the value of the slope, we cannot determine the exact concentration of iron in the sample. Once you have the slope from the calibration curve, you can plug it into the equation above to find the concentration of iron in the sample.