How many female customers have a junior credit card?
Female refers to gender = 'F'
SELECT COUNT(T1.client_id) FROM client AS T1 INNER JOIN disp AS T2 ON T1.client_id = T2.client_id INNER JOIN card AS T3 ON T2.disp_id = T3.disp_id WHERE T1.gender = 'F' AND T3.type = 'junior'