Values of a differentiable function g are recorded every 0.2 units of x at x=a−0.2, x=a, and x=a+0.2. Which of the following estimation schemes is most likely to yield the smallest truncation error when approximating g′(a)?
a) 0.2g(a+0.2)−g(a−0.2)
b) 0.4g(a+0.2)−g(a−0.2)
c) 0.2g(a+0.2)−2g(a)+g(a−0.2)
d) 0.2g(a+0.2)−g(a)