def METHOD_NAME(birth_year):
    """
    given a worker's birth year,
    returns full retirement age in years and months;
    returns None if the supplied year isn't valid
    """
    b_string = yob_test(birth_year)
    if b_string:
        yob = int(birth_year)
        if b_string in age_map.keys():
            return age_map[b_string]
        elif yob <= 1937:
            return (65, 0)
        elif yob >= 1943 and yob <= 1954:
            return (66, 0)
        elif yob >= 1960:
            return (67, 0)
    else:
        return None