F(x)=1 if the decimal expansion of x contains a 5; =0 otherwise.
According to the answer, x is a local minimum point if its decimal expansion does not contain 5.
If I understand the question correctly, if x’s decimal expansion does not contain 5, x should be 0 and every number around it should also be 0 unless x is .49999⋯999 So the correct answer should be either local minimum or both a local minimum and a local maximum