Answer:
Triec, inc., violated the National Labor Relations Act (NLRA) because it directly interfered with the organization of a union within the company.
The NLRA allows private employees to join or form a union, and the company cannot interfere in any of these. E.g. a company cannot fire or punish in any way an employee for joining a union. A company cannot interfere with the creation of a union.
In this case, the company granted the new benefits in order to convince its workers to not form the union.