Find the Function Value $f ( x ) = \left( \frac { 1 } { 6 } \right) ^ { x }$

Multiple Choice

Find the function value. If the result is irrational, round your answer to the nearest thousandth.
-Let $f ( x ) = \left( \frac { 1 } { 6 } \right) ^ { x }$ . Find $f ( 3 )$

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