Find the total number of rooms in the apartments that have facility code "Gym".
SELECT sum(T2.room_count) FROM Apartment_Facilities AS T1 JOIN Apartments AS T2 ON T1.apt_id  =  T2.apt_id WHERE T1.facility_code  =  "Gym"
SELECT sum(T2.room_count) FROM Apartment_Facilities AS T1 JOIN Apartments AS T2 ON T1.apt_id  =  T2.apt_id WHERE T1.facility_code  =  "Gym"
[{'sum(T2.room_count)': 15}]