x1=[7 1 11 11 7 11 3 1 2 21 1 11 10]';
x2=[26 29 56 31 52 55 71 31 54 47 40 66 68]';
y=[78.5 74.3 104.3 87.6 95.9 109.2 102.7 72.5 93.1 115.9 83.8 113.3 109.4]';

X=[ones(13,1) x1 x2];
   b=regress(y,X)