This morning, the teacher who sent us uv printer called us and said that he had come downstairs when I was out of the house and something was not at home. So I asked the teacher to wait a little while and then went home immediately. When I got home, I found that the master who sent uv printer on such a cold day was waiting in front of our house because the car parked far away from our building. It was inconvenient for them to move uv printer up and down. So they were waiting there. I opened the door and gave them a cup of hot water to warm them up and install them again. But the master insisted on installing uv printer for us first. I really admire their professional attitude towards their work.