pre_text: Operating Expense Selling, general and administrative expense increased $9.6 million to $24.4 million for the year ended December 31, 2019 compared to $14.8 million for the year ended December 31, 2018. Selling, general and administrative expense increased primarily due to $4.4 million of expenses associated with the legacy business of MOI and $2.0 million of expenses associated with the legacy business of GP , in addition to $1.0 million in transaction costs associated with the acquisition of GP, a $0.9 million increase in share-based compensation as a result of new awards, and a $1.1 million increase in expenses related to sales and marketing as a result of increased revenue. Research, development and engineering expenses increased $3.7 million to $7.5 million for the year ended December 31, 2019 compared to $3.8 million for the year ended December 31, 2018 primarily due to $1.1 million of research, development and engineering expense associated with the legacy business of MOI and $2.7 million of research, development and engineering expense associated with the legacy business of GP during the year ended December 31, 2019.
table: Years ended December 31,
table: 2019 2018 $ Difference  % Difference
table: Selling, general and administrative expense $24,371,349 $14,794,205 $9,577,144 64.7%
table: Research, development and engineering expense 7,496,012 3,766,160 3,729,852 99.0%
table: Total operating expense $31,867,361 $18,560,365 $13,306,996 71.7%
question: Analyse this data from a financial earnings document. What is the average Research, development and engineering expense for December 31, 2018 and 2019?