Find the Exact Value of the Expression Using the Provided $\sin ( \mathrm { s } - \mathrm { t } )$

Find the exact value of the expression using the provided information.
-Find $\sin ( \mathrm { s } - \mathrm { t } )$ given that $\sin \mathrm { s } = - \frac { 1 } { 2 }$ , with $\mathrm { s }$ in quadrant IV, and $\sin t = \frac { 1 } { 4 }$ , with $t$ in quadrant II.

A) $\frac { - \sqrt { 15 } + \sqrt { 3 } } { 8 }$
B) $\frac { \sqrt { 15 } - \sqrt { 3 } } { 8 }$
C) $\frac { \sqrt { 15 } + \sqrt { 3 } } { 8 }$
D) $\frac { - \sqrt { 15 } - \sqrt { 3 } } { 8 }$