Problem 13.12.9
S = {
3.100 0.101 -0.279 -0.083 -0.009 1.557
0.101 5.780 1.013 -0.114 -1.014 0.039
-0.279 1.013 5.560 1.039 1.366 -0.169
-0.083 -0.114 1.039 5.600 3.080 0.258
-0.009 -1.014 1.366 3.080 6.820 0.272
1.557 0.039 -0.169 0.258 0.222 5.170
}