Find the Function Value $f ( x ) = 6 ^ { x }$

Multiple Choice

Find the function value. If the result is irrational, round your answer to the nearest thousandth.
-Let $f ( x ) = 6 ^ { x }$ . Find $f ( - 3 )$ .

A) $\frac { 1 } { 729 }$
B) $\frac { 1 } { 216 }$
C) $- \frac { 1 } { 18 }$
D) $- 18$