Q: In this task, we ask you to write a question that asks about "event duration", based on a given sentence. The question will likely start with "How long". Your question should be answerable based on the common knowledge of how long certain events usually last. Don't create questions which have explicit mentions of answers in the text. Instead, it has to be implied from what is given. In other words, we want you to use "instinct" or "common sense". Note that the written questions are not required to have a single correct answer.
Sentence: He continued playing and writing notes for half an hour, then went upstairs to his study, where he remained for two weeks, with Elsa bringing up his food.
A:
How long did it take Elsa to prepare his food?