Here we have
$$\left[\begin{array}{}8 &3 &0 &5\\ 0 & 4& 4& 1\end{array}\right]$$
and I heard col2
$$\left[\begin{array}{}3\\4\end{array}\right]$$
is dominated by col3
$$\left[\begin{array}{}0\\4\end{array}\right]$$
and reduced matrix is
$$\left[\begin{array}{}8 &0 &5\\
0 & 4& 1\end{array}\right]$$
but how come?
if every element of the matrix is less, then we can delete the column?
I do not think this is true. It is possibly the other way round, i.e, col 3 is weakly dominated by col 2.