An employer became aware that a union organizing campaign was underway in one of its plants. A union supporter was called in to a meeting with plant managers. At the end of the meeting, when the employee asked what he was supposed to do if others wanted to talk with him about unionizing, he was told “You’re to just work and not talk about the Union.” After union supporters posted material on company bulletin boards, the flyers were repeatedly taken down. The company then issued a policy requiring all employees to obtain approval before placing any material on the boards. Subsequently, the company’s practice was to refuse to post material of any kind from employees. A few months later, several off-duty employees attempted to distribute prounion flyers in the company parking lot but were stopped by company officials. They were warned that they were in violation of company policy. Around the same time, employees passed out union buttons in the plant and left some of them near a time clock for other employees to pick up. When company officials learned of this activity, they quickly called a meeting and warned one union advocate that “I don’t want to catch you passing [buttons] out, Okay, I don’t want to see them laying around. . . . You can pass them out when you’re outside, on your own time, but when you’re here working, you, you, need to be working.” The officials said that this action was taken to keep the plant free of clutter and trash. Has this employer engaged in unfair labor practices in its response to the union organizing activity?