I'm using the code below to concatenate certain sheets in my file into a sheet named "Master".

1. Currently, my script duplicates the header row, but I would like to prevent this. The data in all the sheets is in exactly the same format with the same header.
2. Each sheet has 58 columns and one of the sheets has 5000 rows.
3. Ideally I'd like the script to overwrite the "Master" sheet each time the script is run.

How can I modify my script to accomplish these goals?

```
function concatAllSheets()
{
  var includedSheet = ['Virtue data - Norway - NOK', 'Virtue data - Sweden - SKK', 'Virtue data - Denmark - DKK', 'Virtue Data - GBP', 'Virtue data - EUR markets', 'Virtue data - Arabia - USD'];
  var ss = SpreadsheetApp.getActive();
  var allSheets = ss.getSheets();
  var sheetName = 'Master'
  var mother = ss.insertSheet(sheetName);
  for(var i = 0; i < allSheets.length; i++)
  {
    var sht = allSheets[i];
    if(includedSheet.indexOf(sht.getName()) > -1)
    {
      var rng = sht.getDataRange();
      var rngA = rng.getValues();
      for(var j = 0; j < rngA.length; j++)
      {
        var row = rngA[j];
        mother.appendRow(row);
      }
    }
  }
}

```