Suppose I have a matrix like the following
$$A= \begin{pmatrix} B & y \\ y^{*} & a \\ \end{pmatrix}$$
where $B$ is a Hermitian matrix. How can I prove that
\begin{equation} \lambda_{1}(A)\leq \lambda_{1}(B)\leq \lambda_{2}(A)\leq \dots \leq \lambda_{n}(A)\leq \lambda_{n}(B)\leq \lambda_{n+1}(A) \end{equation}
I know that I should somehow use Weyl inequality. But I don't know how.