For the function \( f : [1,\infty) \to [1,\infty) \) defined \( f(x) = (x-1)^4 + 1 \), among the two statements:
(I) The set \( S=\{x \in [1,\infty) : f(x)=f^{-1}(x)\} \) contains exactly two elements, and
(II) The set \( S=\{x \in [1,\infty) : f(x)=f^{-1}(x+1)\} \) is an empty set,
