Utilize the input text as a context reference, choose the right relationship between 'Mack Trucks' and 'Truck' from the options.
Options: distribution format, founded by, product/material produced, business division

In what was then the largest environmental enforcement case in U.S. history, companies including industry leaders Caterpillar Inc., Cummins Engine Co., Mack Trucks and Volvo Truck Corp. agreed to pay $83.4 million in fines and reprogram the computers.
product/material produced