City Electric sells AAA size batteries through its retail store in Perth. The average demand per week for its AAA batteries is 10,500 units. The weekly standard deviation of demand is 2,750. The company orders batteries in lot sizes of 30,000 units and it takes 3 weeks lead time to replenish an order. If City Electric holds 5000 units in safety stock, what is the average flow time (weeks) of AAA batteries in the system?