def common_members(list_a, list_b):
    """ list_c = common_members(list_a, list_b)
    Return a list (sorted) of common members in list_a, list_b
    
    Parameters:
        list_a: list
        list_b: list
    Returns:
        list_c: a list of common members in list_a and list_b
    
    """
    list_c = list(set(list_a).intersection(list_b))
    list_c.sort()
    return list_c