For two events $A , B$,
$$\mathrm { P } \left( A ^ { C } \right) = \frac { 2 } { 3 } , \quad \mathrm { P } \left( A ^ { C } \cap B \right) = \frac { 1 } { 4 }$$
What is the value of $\mathrm { P } ( A \cup B )$? (Note: $A ^ { C }$ is the complement of $A$.) [3 points]\\
(1) $\frac { 1 } { 2 }$\\
(2) $\frac { 7 } { 12 }$\\
(3) $\frac { 2 } { 3 }$\\
(4) $\frac { 3 } { 4 }$\\
(5) $\frac { 5 } { 6 }$