pre_text: The amount of our operating expenses increased by $43 million on a sequential basis, mainly driven by seasonality and salary dynamic. On a year-over-year basis, our operating expenses increased by $42 million, mainly due to salary dynamic and increased spending on certain R&D programs, partially offset by favorable currency effects, net of hedging. Fourth quarter 2019 R&D expenses were net of research tax credits in France and Italy, which amounted to $37 million, compared to $29 million in the third quarter of 2019 and $39 million in the fourth quarter of 2018.
table: Three Months Ended % Variation
table: December 31, 2019 September 29, 2019 December 31, 2018 Sequential Year-Over-Year
table: (Unaudited, in millions)
table: Selling, general and administrative expenses $(285) $(267) $(285) (6.3)% 0.4%
table: Research and development expenses (387) (362) (345) (7.0) (12.3)
table: Total operating expenses $(672) $(629) $(630) (6.7)% (6.6)%
table: As percentage of net revenues (24.4)% (24.7)% (23.8)% +30 bps -60 bps
question: Analyse this data from a financial earnings document. What is the average Selling, general and administrative expenses for the period December 31, 2019 and September 29, 2019?