A continuous, linear time-invariant filter has an impulse response $h(t)$ described by
$$h(t) = \left\{\begin{matrix}3 &\text{for}\:\: 0 \leq t \leq 3 \\ 0& \text{otherwise} \end{matrix}\right.$$
When a constant input of value $5$ is applied to this filter, the steady state output is ________.