So to continue our previous case study for Y = 0.2, when Ri = 1 we have a predicted value of AY,i = 2 0.5 at |Ri -Y| = 0.8. The line through this point with a power-law slope of -1 is shown in Figure and is a good description of the data. If we substitute Equations 1 and 2 into Equation 11 we obtain a very simple to use expression: