The value of b(opt) equals 5704, which corresponds to the binary number [1011001001000] to be interpreted as geological class 1 (to be counted from the rear), g(1) ¼ 0, hence Rn-prone, etc., class 4,g(4) ¼ 1, hence non-Rn-prone, and so on until g(13) ¼ 1, non prone. Class 1 designs granite, class 4 basalt and class 13 loess.