You Be The Detective - 2
\((1)\) If Rocky is guilty and Bob is innocent, then Mike must be guilty.
\((2)\) Mike never works alone.
\((3)\) Rocky and Mike never work together.
\((4)\) No one other than Rocky, Bob and Mike are involved and at least one of them is guilty.
Only you can help Milind now, to find the person who is necessarily guilty.
This problem is the part of my set Is This What You Call Logic?!