Final answer:
The number 9 in the model number 113902 indicates that the engine has an auxiliary PTO parallel to the crankshaft.
Step-by-step explanation:
The model number 113902 indicates that the engine has a certain characteristic or feature. In this case, the number 9 indicates that the engine has an auxiliary PTO parallel to the crankshaft. This means that the engine is equipped with an additional power take-off system that runs parallel to the crankshaft, which provides flexibility for connecting and powering other machinery or equipment.