Can anyone work this stats problem concerning diminishing returns? I would appreciate any help. Thanks, cool mom

In the axiom "an apple a day keeps the doctor away" if a doctor visit costs $125 on average, at what cost per apple would the practice of this ritual exhibit diminishing returns for a 1-year (365 days) period?

A. $0.14

B. <$0.21

C. >$0.34

D. $0.23

E. >$0.55