Find the Exact Value Under the Given Conditions $\sin \alpha = \frac { 20 } { 29 } , \frac { \pi } { 2 } < \alpha < \pi ; \quad \cos \beta = \frac { 3 } { 5 } , 0 < \beta < \frac { \pi } { 2 } \quad$

Multiple Choice

Find the exact value under the given conditions.
- $\sin \alpha = \frac { 20 } { 29 } , \frac { \pi } { 2 } < \alpha < \pi ; \quad \cos \beta = \frac { 3 } { 5 } , 0 < \beta < \frac { \pi } { 2 } \quad$ Find $\sin ( \alpha - \beta )$ .

A) $\frac { 143 } { 145 }$
B) $- \frac { 17 } { 145 }$
C) $\frac { 144 } { 145 }$
D) $- \frac { 24 } { 145 }$