Find the Indicated Sum $a _ { 1 } = - 5 , r = 3 ; \text { find } s _ { 4 }$

Find the indicated sum.
- $a _ { 1 } = - 5 , r = 3 ; \text { find } s _ { 4 }$

A) 200
B) -65
C) - 200
D) - 40