reserve x for set,
  p,q,r,s,t,u for ExtReal,
  g for Real,
  a for Element of ExtREAL;

theorem :: MEASURE5:40
  r <= p & r <= s implies not [.r,s.] c= ].p,q.]
proof
  assume that
A1: r <= p and
A2: r <= s;
  take r;
  thus r in [.r,s.] by A2,Th1;
  thus thesis by A1,Th2;
end;
