Final answer:
The sales manager's salary is not an element of manufacturing overhead since this role is related to the selling of the product and not its manufacturing.
Step-by-step explanation:
Regarding the question, which of the following is not an element of manufacturing overhead, the correct answer is: (a) Sales manager's salary. Manufacturing overhead encompasses all the indirect costs associated with manufacturing a product except for direct materials and direct labor. Typical elements include the salaries of indirect workers such as factory repairmen and product inspectors, but not sales managers, as their work is related to selling the product, not manufacturing it. The salaries of plant managers and factory repair workers are part of manufacturing overhead since they directly contribute to the production process.