April 2008 Q11 In an investigation about the duration of insurance policies of a certain type, a sample of n policies is studied. All n policies have been initiated at the same time, which is also the time of the start of the investigation. For each policy, the time T (in months) until the policy expires can be modelled as an exponential random variable with parameter λ, independently of the times for all other policies. (i) Suppose that the investigation is terminated as soon as k policies have expired, where k is a known (predetermined) constant. The observed policy expiry times are denoted by t1, t2,
