D1 = H1 - L1 D2 = H2 - L2 D3 = H3 - L3 L1, H1 - the lowest and the highest prices in the Small range L2, H2 - the lowest and the highest prices in the Middle range L3, H3 - the lowest and the highest prices in the Big range K = 100.0 / (1/Small range+1 / Middle range+1 / Big range)