Let I(3m) and I(m) be the approximations of I = Jf(x) da obtained by the composite trapezoid rule using 3m and m sub-intervals respectively. To estimate the truncation error of I(3m ) we use Select one: O a . I(3m)-I(m) 15 O b. I(3m)-I(m) 3 O C. I(3m)-I(m) 9 O d. I(3m)-I(m) 8