Need help computing diminishing returns problem

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

If you suppose that this cost is x, then we need x such that 365*x<125 that is x<.342, so the answer is C