Find the Partial Sum $a _ { n } = \frac { ( - 1 ) ^ { n - 1 } } { 3 n }$

Multiple Choice

Find the partial sum.
-Find the sum of the first four terms of the sequence whose general term is $a _ { n } = \frac { ( - 1 ) ^ { n - 1 } } { 3 n }$ .

A) $- \frac { 7 } { 36 }$
B) $\frac { 7 } { 36 }$
C) $- \frac { 25 } { 36 }$
D) $\frac { 25 } { 36 }$