N = [5.2,2.4,0,-1.7;2.4,7.4,2.3,2.7;0,2.3,6.3,0;-1.7,2.7,0,4.4];
W = -[7;8;6;-3];
K = (inv(N)*W)';
disp(K);
N * inv(N)
[V,D]= eig(N)
abs(N*V-V*D)
b = mean(N)
c = std(N)