Let f(x) = { ((x - 1)sin(1/x -1) if x ≠1), (0 if x = 1) Then which one of the following is true?
(a) f is differentiable at x = 1 but not at x = 0
(b) f is neither differentiable at x = 0 nor at x = 1
(c) f is differentiable at x = 0 and at x = 1
(d) f is differentiable at x = 0 but not at x = 1