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.
Refer to the input text as context and select the correct relationship between 'Volvo' and 'Truck' from the available options.
Options: headquarters location, product/material produced, chief executive officer, manufacturer