申論題

11. (30%) A study show that in an exan the time required to come up with the correct answer for each question is a cont tinuous memoryless random variable with the ex expected value equal to the difficulty level of the question. The time to answer each question is independent of each other.

(e) (6%) 50 students participate in an exam and all of them start with the first question at the same tine. The diffculty level of the first question is 2. What is the probability that the question is answered correctly within 2 time units by any of the 50 students?