reserve x,y,y1,y2 for set;
reserve C for non empty set;
reserve c for Element of C;
reserve f,h,g,h1 for Membership_Func of C;

theorem
  min(h.c,g.c) = min(h,g).c & max(h.c,g.c) = max(h,g).c by Def3,Def4;
