def _beam_angle(serial_number):
    """Get the beam angle from the serial number"""
    if serial_number[1] in "12345678DEFGbcdefghi":
        return 20
    elif serial_number[1] in "OPQRST":
        return 15
    elif serial_number[1] in "IJKLMNjklmnopqrstuvwxy":
        return 30
    elif serial_number[1] in "9ABCUVWXYZ":
        return 0
    print("Could not determine beam angle.")
    return None