if ($possible) {
  $average = sprintf("%2.2f", ($earned / $possible) * 100);

  if    ($average >= 95) { $grade = "A";  }
  elsif ($average >= 90) { $grade = "A-"; }
  elsif ($average >= 87) { $grade = "B+"; }
  elsif ($average >= 84) { $grade = "B";  }
  elsif ($average >= 80) { $grade = "B-"; }
  elsif ($average >= 77) { $grade = "C+"; }
  elsif ($average >= 74) { $grade = "C";  }
  elsif ($average >= 70) { $grade = "C-"; }
  elsif ($average >= 67) { $grade = "D+"; }
  elsif ($average >= 64) { $grade = "D";  }
  elsif ($average >= 60) { $grade = "D-"; }
  elsif ($average <  60) { $grade = "E";  }

} else {

  $grade = $average = $earned = $possible = "?";
}