Consider the following table. Determine the most accurate method to approximate f'(0.2), f'(0.4), f'(0.8), ƒ"(1.1).
X1 0 0.2 0.4 0.5 0.7 0.8 0.9 1.1 1.4 1.5
F (x2) 0 0.2399 0.3899 0.7474 0.9522 1.397 1.624 2.035 2.325 2.278