The Graph of a Function F Is Given $f ^ { - 1 } ( x )$

The graph of a function f is given. Use the graph to find the indicated value.
-Let f(x) compute the cost of a rental car after x days of use at $50 per day. What is the interpretation of the solution of $f ^ { - 1 } ( x )$ = 184?

A) The cost of rental for 50 days
B) The number of days rented for $184
C) The cost of rental for 184 days
D) The number of days rented for $50