Write SQL query to solve given problem: How many female actors acted in the movies of year 4?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT COUNT(T2.actorid) FROM movies AS T1 INNER JOIN movies2actors AS T2 ON T1.movieid = T2.movieid INNER JOIN actors AS T3 ON T2.actorid = T3.actorid WHERE T3.a_gender = 'F' AND T1.year = 4