function validate_qty(f) {
  var teachers = Number(document.getElementById('S02').value);
  if (teachers < 1 || isNaN(teachers)) {
    teachers = 1;
    document.getElementById('S02').value="1";
  }
  if (isNaN(f.value)) {
    f.value="0";
    alert('Quantities must be whole numbers expressed as numerals');
  }
  var p1 = Number(document.getElementById('P41045').value);
  var p2 = Number(document.getElementById('P37030').value);
  var p3 = Number(document.getElementById('P37050').value);
  var p4 = Number(document.getElementById('P37055').value);
  var p5 = Number(document.getElementById('P37060').value);
  var total = p1 + p2 + p3 +p4 + p5;
  if ((total / teachers) > 42) {
    alert('Sorry, quantities are restricted to 35 booklets per educator.');
    f.value = "";
    if (f.id == 'S02') {
      document.getElementById('P41045').value="0";
      document.getElementById('P37030').value="0";
      document.getElementById('P37050').value="0";
      document.getElementById('P37055').value="0";
      document.getElementById('P37060').value="0";
    }
  }
  if (total == "0") {
    alert('Please enter quantities for the books you wish to order');
  }
}