Using the point H_a and the point M_b, construct a circle k(M_b,C) (rule W06);

% NDG: points H_a and M_b are not the same

Choose freely a point C on the circle k(M_b,C) (rule WOncircle)

Using the point C and the point M_b, construct a point A (rule W01);

Using the point C and the point H_a, construct a line a (rule W02);

% DET: points C and H_a are not the same

Choose freely a point B on the line a (rule WOnline1)