Good day guys, I just need some advice on how to determine the difference between a singular and a non singular matrix. Also would it be correct if I classified the matrix below as a reduced row echelon form because each leading 1 is to the right of the previous and there is a zero above and below every leading one?

A=

1 2 0 0

0 0 1 0

0 0 0 1

Kind regards

Hyperion