Find the Exact Value Under the Given Conditions Find $\sin ( \alpha - \beta )$

Multiple Choice

Find the exact value under the given conditions.
- $\sin \alpha = - \frac { 3 } { 5 } , \frac { 3 \pi } { 2 } < \alpha < 2 \pi ; \quad \cos \beta = - \frac { \sqrt { 21 } } { 5 } , \pi < \beta < \frac { 3 \pi } { 2 } \quad$ Find $\sin ( \alpha - \beta )$

A) $\frac { - 6 - 4 \sqrt { 21 } } { 25 }$

B) $\frac { - 8 + 3 \sqrt { 21 } } { 25 }$

$\frac { - 6 + 4 \sqrt { 21 } } { 25 }$

D) $\frac { 8 + 3 \sqrt { 21 } } { 25 }$