A function g has the following features on the interval (−6,6):
• a sharp corner at x=−1
• a vertical tangent at x=2
• a removable discontinuity at x=5
• no other singular behavior
At which of the following x–values is g NOT differentiable?
a) x=−1 and x=2 only
b) x=−1 and x=5 only
c) x=−1,x=2, and x=5
d) x=2 and x=5 only