Exercise 3.3.14

The input-output matrix $A$ should be $\left(\begin{array}{cc}\hfill 0.50\hfill & \hfill 0.20\hfill \\ \hfill 0.30\hfill & \hfill 0.60\hfill \end{array}\right)$. And the demand vector $d$ should be $\left(\begin{array}{c}\hfill 90\hfill \\ \hfill 20\hfill \end{array}\right)$. So we can solve the equation $(I-A)x=d$ and get the answer $x=(\frac{2000}{7},\frac{1850}{7})$. Thus $x$ is the support vector.