3. The events \(A\) and \(B\) are such that $$\mathrm { P } ( A ) = \frac { 7 } { 12 } , \mathrm { P } ( A \cap B ) = \frac { 1 } { 4 } \quad \text { and } \mathrm { P } ( A \mid B ) = \frac { 2 } { 3 }$$ Find

1. \(\mathrm { P } ( B )\),
2. \(\mathrm { P } ( A \cup B )\),
3. \(\mathrm { P } \left( B \mid A ^ { \prime } \right)\).