Lviv is also one of the leaders of software export in Eastern Europe with expected sector growth of 20% by 2020. Over 25% of all IT specialists in Ukraine work in Lviv, with over 1500 new IT graduates coming from local universities each year. In 2009, [KPMG], one of the famous international auditing companies, included Lviv in top 30 cities with the greatest potential of information technology development.  As of December 2015, there were 192 IT-companies operating in the city, of which 4 large (with more than 400 employees), 16 average (150-300 employees), 97 small (10-110 employees) and 70 micro companies (3-7 employees). The turnover of the Lvivs IT industry in 2015 amounted to $ 300 million U.S. About 50% of IT services are exported to the US, 37% to Europe, and the rest - to other countries. As of 2015, about 15 thousand specialists were employed in this industry with the average salary of 28 thousand UAH. According to a study of the Economic Effect of the Lviv IT-Market, which was conducted by Lviv IT Cluster and sociological agency "The Farm", there are 257 IT companies operating in Lviv in 2017, that employing about 17 thousand specialists. The economic impact of the IT industry in Lviv is $ 734 million U.S..
Question: How many total large and average size IT companies are operating in Lviv as of 2015?
Answer: 20