reserve c,c1,c2,x,y,z,z1,z2 for set;
reserve C1,C2,C3 for non empty set;

theorem
  for c be Element of [:C1,C2:] holds (Zmf(C1,C2)).c = 0 & (Umf(C1,C2)).
  c = 1 by FUNCT_3:def 3;
