pre_text: Net revenue: Net revenue from our Energy segment for the year ended December 31, 2019 increased $18.3 million to $39.0 million from $20.7 million for the year ended December 31, 2018. The increase was primarily driven by the AFTC related to the 2018 and 2019 CNG sales that was recognized in the fourth quarter of 2019, inclusive of prior period AFTC at the acquired ampCNG stations which was also recognized in 2019. The increase was also driven by higher volume-related revenues from the recent acquisition of the ampCNG stations and growth in CNG sales volumes. Cost of revenue: Cost of revenue from our Energy segment for the year ended December 31, 2019 increased $5.9 million to $17.1 million from $11.2 million for the year ended December 31, 2018. The increase was due to overall growth in volumes of gasoline gallons delivered and higher commodity and utility costs driven by the acquisition of ampCNG stations. Selling, general and administrative: Selling, general and administrative expenses from our Energy segment for the year ended December 31, 2019 increased $0.9 million to $4.9 million from $4.0 million for the year ended December 31, 2018. The increase was driven by an increase in salaries and benefits largely due to the of the acquisition of ampCNG stations, which were acquired late in the second quarter of 2019, partially offset by a one-time expense in the prior year related to the abandonment of a station development project. Depreciation and amortization from our Energy segment for the year ended December 31, 2019 increased $1.4 million to $6.9 million from $5.5 million for the year ended December 31, 2018. The increase was due to additional depreciation and amortization from the recent acquisition of ampCNG stations. Other operating expense from our Energy segment was a loss of $0.5 million for the year ended December 31, 2018, driven by impairment of certain stations during the fourth quarter of 2018.
table: Years Ended December 31,
table: 2019 2018 Increase / (Decrease)
table: Net revenue $39.0 $20.7 $18.3
table: Cost of revenue 17.1 11.2 5.9
table: Selling, general and administrative 4.9 4.0 0.9
table: Depreciation and amortization 6.9 5.5 1.4
table: Other operating expense — 0.5 (0.5)
table: Income (loss) from operations 10.1 $(0.5) $10.6
question: Analyse this data from a financial earnings document. What was the average cost of revenue?