Final answer:
According to the principle of 'sale of an apartment includes everything in it,' Jan would have the legal right to keep the valuable drawings she discovered in the closet after moving into the apartment.
Step-by-step explanation:
According to the principle of 'sale of an apartment includes everything in it,' Ron would not prevail in the suit to get the drawings back. This principle means that when a person sells an apartment, they are also selling everything inside it unless there is a specific agreement stating otherwise. In this case, Jan discovered the drawings after moving in, which means they were included in the sale of the apartment. Therefore, Jan would have the legal right to keep the valuable drawings.