Utilize the input text as a context reference, choose the right relationship between Mack Trucks and Truck from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

In what was then the largest environmental enforcement case in US history, companies including industry leaders Caterpillar Inc, Cummins Engine Co, Mack Trucks and Volvo Truck Corp agreed to pay $US83.4 million in fines and reprogram the computers.

Answer: product_or_material_produced