Let $z$ and $w$ be complex numbers lying on the circles of radii 2 and 3 respectively, with centre ( 0,0 ). If the angle between the corresponding vectors is 60 degrees, then the value of $| z + w | / | z - w |$ is:\\
(A) $\frac { \sqrt { 19 } } { \sqrt { 7 } }$\\
(B) $\frac { \sqrt { 7 } } { \sqrt { 19 } }$\\
(C) $\frac { \sqrt { 12 } } { \sqrt { 7 } }$\\
(D) $\frac { \sqrt { 7 } } { \sqrt { 12 } }$.