Find an Equation for the Rational Function Graph $\mathrm { f } ( \mathrm { x } )$

Find an equation for the rational function graph.
-In the following formula, $\mathrm { f } ( \mathrm { x } )$ is the minimum number of hours of studying required to attain a test score of $x : f ( x ) = \frac { 0.48 x } { 100.5 - x }$ . How many hours of study are needed to score $85 ?$

A) $26.30 \mathrm { hr }$
B) $2.63 \mathrm { hr }$
C) $100.93 \mathrm { hr }$
D) $5.18 \mathrm { hr }$