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

Find the exact value of the expression using the provided information.
-Find $\tan ( \mathrm { s } + \mathrm { t } )$ given that $\cos \mathrm { s } = - \frac { 12 } { 13 }$ , with $\mathrm { s }$ in quadrant II, and $\sin t = \frac { 8 } { 17 }$ , with $t$ in quadrant II.

A) $- \frac { 171 } { 221 }$
B) $- \frac { 171 } { 220 }$
C) $- \frac { 171 } { 140 }$
D) $\frac { 3 } { 20 }$