Var tc,d,i:longint;
    num1, denum1, a, p, q:extended;
    num, denum:int64;
 function z(x:extended):boolean;
   begin
     z:=(abs(x - round(x)) < 1e-9);
   end;
  begin
    read(tc);
    while tc>0 do
      begin
        dec(tc);
        read(a,p,q,d);
        num1:=p*a*(1 - a) + q * a;
        denum1 := (1 - a) * (1 - a);
        while (z(num1) = false )or(z(denum1) = false) do
          begin
            num1 := num1 * 10;
            denum1 := denum1 * 10;
          end;
        num := round(num1);
        denum := round(denum1);
        Write(num div denum,'.');
        num:=(num mod denum)*10;
        for i:=1 to d do
          begin
            if num < denum then
              begin
                num:=num * 10;
                Write(0);
                continue;
              end;
            Write(num div denum);
            num := num mod denum;
            num := num * 10;
          end;
        Writeln;
      end;
  end.

  p*a(1 - a) + q*a/
  (1-a) ^ 2

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