Hilpa's gym membership includes a one-time fee of $20. She then pays a discounted fee of $5 for each visit. The function that shows her average cost after x visits is:

f (x) = StartFraction 20 + 5 x Over x EndFraction

Recall the general form of a rational function:

f (x) = StartFraction (a m x Superscript m Baseline + ellipsis + a 1 + a 0) Over (b n x Superscript n Baseline + ellipsis + b 1 x + b 0)

Which statement defines the horizontal asymptote?