need the Upper control limit & lower control limit

Sampling 4 pieces of precision-cut wire (to be used in computer assembly) every hour for the past 24 hours has produced the following results: Based on the sampling done, the control limits for 3 -sigma x chart are (round all intermediate calculations to three decimal places before proceeding with further calculations): Upper Control Limit (UCL Ux)= inches (round your response to three decimal places)