Suppose I have a matrix $C=\begin{bmatrix} 1 & 0 \end{bmatrix}$ and a vector $\mathbf{x}=\begin{bmatrix} x_1 \\ x_2 \end{bmatrix}$.
I want to write the matrix product $C\mathbf{x}$, should the answer be vector notation (bold) or not?
I mean vector notation $$\mathbf{y}= C\mathbf{x}=\begin{bmatrix}1 & 0\end{bmatrix}\begin{bmatrix} x_1 \\ x_2 \end{bmatrix}=x_1 $$ or scalar notation $$ y= C\mathbf{x}=\begin{bmatrix}1 & 0\end{bmatrix}\begin{bmatrix} x_1 \\ x_2 \end{bmatrix}=x_1 $$ I use upright letters for matrices, bold letters for vectors. Non-bold for scalars.