% actual value given by the textbook
exact = 6.74*10^-3;

% excute h1_11b & h1_11c to get answer_b
% and answer_c
h1_18a
h1_18b

% relative error = |p-p*|/|p| where p is the 
% exact solution and p* is an approximation to p
rel_1 = abs(exact-sum1)/abs(exact)
rel_2 = abs(exact-sum2)/abs(exact)