Here's a short story:

Joe was an old man. The 75-year-old lived very happily in a village and had a beautiful family. Joe had four grandchildren, and they visited him during their holidays. During one vacation, Joe was preparing his home for the kids: cleaning and buying their favorite foods. After he finished working, he realized he lost his favorite watch. The watch was a gift from his wife when their first child was born. Joe loved the watch very much, especially after his wife's death. He was very upset about losing it. Once his grandchildren came, they promised him they would find the watch. One granddaughter asked: "Grandpa, do you remember when you saw the watch last before it went missing?" "I guess when I was cleaning the barn !" Joe replied. The children looked for more than two hours with Joe, but they could not find it. The kids were now also sad, but they tried to comfort their grandfather. One grandson went back to the barn to search again. Joe asked why he was going there a second time. But the little boy just asked the others not to follow him and to remain silent. He was there for about fifteen minutes and then rushed to his grandfather. He found the watch and happily gave it to Joe. Joe was surprised and asked how he was able to find it. The little boy replied: "I sat there without making a noise, and the barn was so silent. After a few minutes, I heard the 'tick, tick' sound and found the watch." Joe hugged and thanked the little boy. (End of story)

Provide your best guess for the following question. Give ONLY the guess, no other words or explanation.

For example:

Guess: <most likely guess, as short as possible; not a complete sentence, just the guess!>

Here are a few examples of questions and answers:

Question: What did Joe lose?
Guess: his favorite watch

Question: How old is he?
Guess: 75

Question: Who found it?
Guess: One of his grandsons

Question: Was he old?
Guess: No

Question: Did he make a lot of noise when finding it?
Guess: No

Question: How long did it take him to find it?
Guess: about fifteen minutes

Question: What did he hear?
Guess: 'tick, tick'

Question: Where did he find it?
Guess: the barn

Question: Had they looked there before?
Guess: Yes

Now answer the following question in the same format.

Question: For how long?

two hours