When was the customer survey conducted? It was conducted______.

Now I’m going to tell you the result of [16]the customer survey we conducted last month. We got high marks from our customers about the quality of our products. [17]They felt our products were quite reliable and carried a lot of the features they expected in electronics. They especially liked the high-tech mobile phone which combines our mobile phone with a camera and MP3 player. However, customers were not satisfied with our customer service. They complained in the survey that [18]it took too long to settle their complaints. They also complained that [19]our service staff were not always friendly. By contrast, they wrote that many of our competitors have excellent customer service. This is the urgent task we have to deal with now. That’s why I’m ordering the customer service department to [20]come up with a plan within one week, and I also ask them to explain how they intend to improve our customer service.