Assignment:
A unit for a telecommunications system is to be designed so as to have a minimum availability of 0.9994. The MTTR (mean time to repair) for the unit is estimated to be 24 hours. The unit is to consist of (n) effectively identical elements in parallel, from a reliability point of view. If the hazard rate of each of the elements is 5x(10 to the power -5) per hour, estimate the minimum value of (n) which is needed if the unit is to meet the availability specification assuming that the elements are repaired only when the whole system fails.