For f(x)=∣x∣ on the interval [−1,1], why does no point c∈(−1,1) satisfy f′(c)=1−(−1)f(1)−f(−1)?
a) f is not differentiable at the endpoints x=−1 and x=1
b) Because f′(x) on (−1,1) is either 1 or −1, it can never equal the required average rate of change 0
c) f is not differentiable at x=0
d) f is not monotonic on the interval [−1,1]