Answer
$v = (3,4,5)^\top$, $50$, $\texttt{Error}$
Work Step by Step
Since $A$ is the identity matrix, $Av = v$ for all vectors $v$ in $\mathbb{R}^3$. Thus, $Av = v = (3,4,5)^\top$.
$v' \cdot v$ is equal to $v^\top v$. This can be expanded to get
$$v^\top v = v_1^2 + v_2^2 + v_3^2= 3^2+4^2+5^2=50$$
Lastly, since $v$ is $3$ by $1$ and $A$ is $3$ by $3$, $v A$ is undefined (matrix multiplication cannot be done). Thus, you should get an error when trying to compute $vA$.
