P₉ = (λ₁₀₀/λ₉₁₀)P₁₀

P₈ = ((λ₁₀₀(λ₉₁₀ + λ₉₈))/(λ₈₉λ₉₁₀))P₁₀

P₇ = (λ₁₀₀(λ₉₁₀ + λ₉₈)(λ₈₇ + λ₈₉ - 2λ₉₈(λ₈₉/(λ₉₁₀ + λ₉₈))))/(λ₇₈λ₈₉λ₉₁₀)P₁₀