Exercise 3.5.8

$\left[\begin{array}{cc}I\hfill & 0\hfill \end{array}\right]$and $\left[\begin{array}{cccc}I\hfill & I;\hfill & 0\hfill & 0\hfill \end{array}\right]$and $[0]=3$ by 2 have row space dimensions $=3,3,0=$ column space dimensions; nullspace dimensions $2,3,2$; left nullspace dimensions $0,2,3$.