reserve a,b,c,d for Real;
reserve r,s for Real;

theorem
  b <= a & a <= 0 implies a/b <= 1
proof
  assume
A1: b <= a;
  assume a <= 0;
  then per cases;
  suppose a = 0;
    hence thesis;
  end;
  suppose
A3: a < 0;
    then a/b <= b/b by A1,Lm30;
    hence thesis by A1,A3,XCMPLX_1:60;
  end;
end;
