Calculate the confidence level of this interval. John rings a church bell 120 times. The time interval, Ti, between two successive rings is a random variable with mean of 2 seconds and variance of 1/9 seconds². Each time interval, Ti, is independent of the other time intervals. Let X = Σ Ti be the total time between the first ring and the last ring. Find E(X) and Var(X). Explain why a normal distribution can be used to approximate X. Find values A and B such that P(A < X < B) = 0.9, where A and B are symmetrical about the mean of X. The church vicar suspects someone else is ringing the bell and conducts a hypothesis test.