Evaluate the Given Function $$f ( x ) = 2 ^ { - x } , f ( 9 )$$

Evaluate the given function.
- $$f ( x ) = 2 ^ { - x } , f ( 9 )$$

A) $- 512$
B) $\frac { 1 } { 512 }$
C) $\frac { 1 } { 18 }$
D) $\frac { 2 } { 9 }$