The reasonable value of the range would depend on a variety of factors, such as the difficulty of the exam, the amount of material covered, and the level of preparation of the students. However, as a general guideline, a reasonable range for the number of hours studied for an exam might be around 10 to 20 hours. This would suggest that students are putting in a reasonable amount of effort and time to prepare for the exam, without overdoing it or under-preparing.