Iterate through named range and update values

I need to iterate through a named range in Google Sheet and update the value based on other named ranges.

I have this now and I'm getting an error on line 13

function onEdit(e) {
  var ss = SpreadsheetApp.getActiveSpreadsheet();

  var FreeCopiesTarget = ss.getRangeByName('FreeCopiesTarget');
  var CostPerCopy = ss.getRangeByName('CostPerCopy');
  var FreeCopies = ss.getRangeByName('FreeCopies');

  var values = FreeCopiesTarget.getValues();

 for (var counter = 0; counter <= 4; counter++) {
   var cost = CostPerCopy.getValues()[counter][0] * FreeCopies.getValues()[counter][0];
   var r = FreeCopiesTarget.getValues()[counter][0];
   r.setValue(cost);
 }
}

Any help is appreciated.

Following Iamblichus answer, I tweaked as follows and it works as expected.

function onEdit() {
  var ss = SpreadsheetApp.getActiveSpreadsheet();

  var FreeCopiesTarget = ss.getRangeByName('FreeCopiesTarget');
  freeCopiesValues = FreeCopiesTarget.getValues();
  var CostPerCopy = ss.getRangeByName('CostPerCopy').getValues();
  var FreeCopies = ss.getRangeByName('FreeCopies').getValues();
  
  for (var counter = 0; counter <= 4; counter++) {
    var cost = CostPerCopy[0][counter] * FreeCopies[0][counter];
    freeCopiesValues[0][counter] = cost;
  }
  FreeCopiesTarget.setValues(freeCopiesValues);
}