In the plot of Absorbance vs concentration, we use the Beer-Lambert's Law, given by:
Its graphic is a line in the plane, where A (absorbance) is the dependent variable, c (concentration) is the independent variable, and the terms b are the slope of the line.
The equation (1) has the general form for a linear function with an intercept of zero, and a slope given by the equation:
For a pair of points
In this case, we will have the slopes:
We will have an average of:
According to the data given and the units of the constants.