Suppose that $M_{22}$ is a vector space of all $2 \times 2$ square matrices. Let $U_{22}$ be the set of all upper triangular $2 \times 2$ matrices. Show that $U_{22}$ is a subspace of $M_{22)$ by showing that $U_{22}$ is the span of some set of vectors from $M_{n} $ or by verifving that $U_{n}$ satisfies the three subsbace broberties. Make sure to state the CS.VS. 1416