Here's the exercise filled out based on the provided format:

0. Class 5A/first floor
⇒ Where's Class 5A? - It's on the first floor.

1. Music room/ second floor
⇒ Where's the music room? - It's on the second floor.

2. Art room/ third floor
⇒ Where's the art room? - It's on the third floor.

3. Computer room/ fourth floor
⇒ Where's the computer room? - It's on the fourth floor.

4. Gym/ ground floor
⇒ Where's the gym? - It's on the ground floor.

5. Library/ first floor
⇒ Where's the library? - It's on the first floor.

6. Class 5B/ fifth floor
⇒ Where's Class 5B? - It's on the fifth floor.