Using the point M_c and the point N, construct a circle k(N,M_a) (rule W06);

% NDG: points M_c and N are not the same

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

Choose freely a point A (rule free)

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

Using the point A and the point M_c, construct a point B (rule W01);