Figure 8. Simplified model.

The model is identical to the model shown in Figure 3 with the exception that the weights are approximated with a geometric sequence with the common ratio α, subject to the constraint ∑ _i w _i = 1. This way, $w_1=\frac{1}{1+\alpha +{\alpha }^2}\text{,}$ w ₂ = αw ₁ and w ₃ = αw ₂.