Thank you, Sheng. This is Su Peng. I believe for the first question, for acquisition cost for the adult and kid whole business in the Q4 last year, in 2019, maybe compared with the Q3, we see the cost fully decreased in the cost that we've guided for new student acquisition. It's decreased season over season. That's because – firstly, that's because of seasonality issues. And for the – all the education business, always the summertime is, so they will be the most expensive seasons for the – to acquire new users. And secondly, we believe for the adult and the K-12 student acquisitions, we expect that in the future, so we do see the decreased trend. But we – right now, we don't know if it's a long-term trend or mid or short term. It's only the short-term performance of the market. So we will keep our eye to the market, and we expect to see more and – the results from the market, and again, get back to you to give you more information about the customer acquisition cost, it's trend in the future. And for your second question about how to – our teacher contributions. We believe our faculty and the kind of business structure, first, has been significantly optimized to better reflect the industry standards. We also maintain a highly competitive planning risk we believe, therefore, we retained the top talents. So that's definitely the most important thing for everyone. And also in the Q4, our top 20 instructors contribute about 73% of our revenues from the Youdao Premium courses. And first, it's not only the teachers – individual teachers because they all have the teams, so that shows the team's effort. It's not only the – only one teacher. So as we expect to hire more instructors, we expect the concentration will be come down in the longer term. So currently, we only have the two instructors as doing the revenue share models. And most of the – some teachers, their – the service contract will be ended in the December 31 – as of December 31, 2019. So we – all of them have renewed a new contract with us. We expect it will drag down our gross margin in the future. And we also in the – we also standardized and protected our content of the many performance structure. So we believe in the future, we will provide standardized – more standardized and content and product to our students. I hope that will be helpful. Thank you.