function buildDriveInventory($inventory) {
  $type = [1, 2, 4, 6, 8, 10, 12, 14, 16];
  $unit = "lbs";

  //create new array to hold values
  $new_values = [];

  foreach ($type as $type_value) {
    foreach ($inventory as $product) {
      if ($type_value === $product['capacity']) {
        $new_values[$product['capacity'].$product['unit']] = $product['total'];
      } else {
        $new_values[$type_value.$unit] = 0;
      }
    }
  }

  return $new_values;

}