A bouncing toy reaches a height of \( 64 \) inches at its first peak, \( 48 \) inches at its second peak, and \( 36 \) inches at its third peak. Which explicit function represents the geometric sequence of the heights of the toy?
\( f ( x ) = 48 ( \frac { 5 } { 6 } ) ^ { x - 1 } \)
\( f ( x ) = 48 ( \frac { 3 } { 4 } ) ^ { x - 1 } \)
\( f ( x ) = 64 ( \frac { 3 } { 4 } ) ^ { x - 1 } \)
\( f ( x ) = 64 ( \frac { 5 } { 6 } ) ^ { x - 1 }\)