Create a spreadsheet to design and analyze a shaft to support a spur gear. Select gear from a catalog (McMaster Carr is a good one). Set up a shaft design with an appropriate shoulder to locate the gear. In the spreadsheet, create a parametric model that will allow you to modify fillet radii, stock shaft diameter, length of the shaft, etc. The model should be capable of calculating bending stress, and "worst-case" deflection angle and displacement. You may assume the minimum shaft diameter as a constant diameter for deflection purposes. Use the actual diameters for the stress calculations. Provide a write up describing how to use the model.