Auto pistons at Wenming Chung's plant in Shanghai are produced in a forging process, and the diameter is a critical factor that must be controlled. From sample sizes of pistons produced each day, the mean and the range of this diameter have been as follows: Day Mean (mm) Range R (mm) 1 2 3 4 5 Part 2 a) What is the value of ? enter your response here mm (round your response to two decimal places)