What is the average Research and development funding for the period December 31, 2019 and 2018?
{"": {"December 31, 2019": "", "September 29,2019": "(Unaudited, in millions)", "December 31, 2018": ""}, "Research and development funding": {"December 31, 2019": 68, "September 29,2019": 14, "December 31, 2018": 19}, "Phase-out and start-up costs": {"December 31, 2019": -16, "September 29,2019": -15, "December 31, 2018": -1}, "Exchange gain (loss), net": {"December 31, 2019": 1, "September 29,2019": -1, "December 31, 2018": "\u2014"}, "Patent costs": {"December 31, 2019": -1, "September 29,2019": -1, "December 31, 2018": -1}, "Gain on sale of non-current assets": {"December 31, 2019": 1, "September 29,2019": "\u2014", "December 31, 2018": 1}, "Other, net": {"December 31, 2019": 1, "September 29,2019": 1, "December 31, 2018": -2}, "Other income and expenses, net": {"December 31, 2019": 54, "September 29,2019": -2, "December 31, 2018": 16}, "As percentage of net revenues": {"December 31, 2019": 2.0, "September 29,2019": -0.1, "December 31, 2018": 0.6}}
rd_fund_2019 = df["Research and development funding"]["December 31, 2019"]
rd_fund_2018 = df["Research and development funding"]["December 31, 2018"]
net_revenue_2019 = df["As percentage of net revenues"]["December 31, 2019"]
answer = (rd_fund_2019 + rd_fund_2018) / net_revenue_2019