Answer: researching
designing a product
designing machines to make a product selling a product
Step-by-step explanation:
Mechanical engineers are professionals which can design and manufacture the machine using tools. Before production they undergo thorough research on materials that can become available for production, labor required, design and working of the machine. They design a machine in a way to sale it as a finished product. The mechanical engineers can produce aircraft engines, gas turbines, fuel cells, and machine tools.