A mechanical assembly. A mechanical assembly (Figure) consists of a rod with a bearing on each end. The three parts are manufactured independently, and all vary a bit from part to part.
The length of the rod has mean 12 centimeters (cm) and standard deviation 0.004 millimeters (mm). The length of a bearing has mean 2 cm and standard deviation 0.001 mm. What are the mean and standard deviation of the total length of the assembly?