Introduction to linear operators

Suppose we have a linear operator $\mathcal{B}$, which matrix is $\begin{pmatrix} 3 & -1 \\ 2 & 4 \end{pmatrix}$, and a vector $v = (3, 0)$. What $\mathcal{B}v$ is equal to?

1) It is not a linear operator.

2) $\begin{pmatrix} 9 \\ 6 \end{pmatrix}$;

3) $\begin{pmatrix} 8 \\ 2 \end{pmatrix}$;

4) $\begin{pmatrix} 9 & 0 \\ 6 & 0 \end{pmatrix}$.