Gagal membuat fom perhitungan

Saya membuat form perhitungan otomatis tapi saat saya memasukkan satu inputan berhasil tapi inputan sebelumnya tidak bisa menghitung otomatis jadi hanya salah satu yang bisa dipakai hitung otomatis

<tr>
                   <td width="20%" align="right">Fee Dealer</td>
                    <td>
                    <input type="text" id="txt1"  onkeyup="sum();" />
<input type="text" id="txt2" value="0.0035"  onkeyup="sum();" />
<input type="text" id="txt3" name="feedealer" size="50%" value="<?php echo $fd; ?>" />

<script>
function sum() {
      var txtFirstNumberValue = document.getElementById('txt1').value;
      var txtSecondNumberValue = document.getElementById('txt2').value;
      var result = parseFloat(txtFirstNumberValue) * parseFloat(txtSecondNumberValue);
      if (!isNaN(result)) {
         document.getElementById('txt3').value = result;
      }
}
</script>
</td>
                </tr>
                 <tr>
                    <td width="20%" align="right">Fee VIP</td>
                    <td>
                    <input type="text" id="tt1"  onkeyup="sum();" />
<input type="text" id="tt2" value="0.003"  onkeyup="sum();" />
<input type="text" id="tt3" name="feevip" size="50%" value="<?php echo $fvip; ?>" />

<script>
function sum() {
      var ttFirstNumberValue = document.getElementById('tt1').value;
      var ttSecondNumberValue = document.getElementById('tt2').value;
      var result = parseFloat(ttFirstNumberValue) * parseFloat(ttSecondNumberValue);
      if (!isNaN(result)) {
         document.getElementById('tt3').value = result;
      }
}
</script>
</td>
                </tr>