A_Bi=[ 1 0 -1               % inverse basis matrix
1 1 -3
-1 0 2];
b=[36;32;22];               %  RHS
eps1=-2+rand*10;            % random element in range of b_1
eps2=-2+(1/rand);         % random element in range of b_2
eps3=-4+rand*(4+2/3);         % random element in range of b_3
disp(['random elements in the 3 intervals are :',num2str([eps1 eps2 eps3])]);
random elements in the 3 intervals are :2.1027    -0.88099     -3.7298
theta=rand(3,1);
theta=theta/sum(theta);      % constants for convex combination
deltab=theta.*[eps1 eps2 eps3]'

deltab =

    0.6310
   -0.6092
   -0.0313

newbbar=A_Bi*(b+deltab)

newbbar =

   14.6623
    2.1156
    7.3065

diary off