Problem $5(20$ points$)$: An LTI system has four poles at $-3,-1$ j$,+2$ and two zeros at $1$ and $3.$ a$)$ Indicate all possible ROCs that can be associated with this zero$-$pole pattern. Justify your answer properly. b$)$ For each possible ROC that you identified in part $($a$),$ specify whether the associated system is stable and$/$or causal