How many patients who were female got white blood cells that were below 3.5?
female refers to SEX = 'F'; white blood cells that were below 3.5 refers to WBC < 3.5
SELECT COUNT(T1.ID) FROM Patient AS T1 INNER JOIN Laboratory AS T2 ON T1.ID = T2.ID WHERE T2.WBC < 3.5 AND T1.SEX = 'F'