def pick_term(xp: int, yp: int, zp: int, option: str) -> int:
    """For parm tuple of (x, y, z) and option string like 'x" or '-z'. Return the number for the option term."""
    options_map = {'x': xp, 'y': yp, 'z': zp, '-x': -xp, '-y': -yp, '-z': -zp}
    return options_map[option]