X for x 4 Let f be the piecewise function defined above. Which of the following statements is true? Of is differentiable for all values of x. Of is differentiable for all values of x except x = 1. Of is differentiable for all values of x except x = 4. Of is differentiable for all values of x except x = 1 and x = 4. Of is differentiable for all values of x except x = 1, x = 2, and x = 4