unevaluated leasehold costs and $0.4 million for the acquisition of seismic data. Our 2012 exploration cost consisted of $61.3 million of impairments of unevaluated leasehold costs and $0.1 million for the acquisition of seismic data. Depreciation, depletion and amortization expense (“DD&A”). DD&A of $337.1 million decreased by $6.8 million (2%) from DD&A of $343.9 million in 2012. Our DD&A rate per Mcfe produced averaged $4.83 in 2013 as compared to $3.76 for 2012. The decrease in DD&A primarily resulted from the decline in our natural gas production during 2013, which was partially offset by the increased development costs per Mcfe associated with the oil wells drilled in 2013 and the reduction in proved undeveloped natural gas reserves recognized in 2012 which increased our per unit DD&A rate on our natural gas properties. General and administrative expenses. General and administrative expense of $34.8 million for 2013 was 3% higher than general and administrative expense of $33.8 million for 2012. Stock based compensation decreased by $0.9 million to $12.8 million in 2013 as compared to $13.7 million in 2012. Impairment of oil and gas properties. We recorded impairments to our oil and gas properties of $0.7 million and $25.4 million in 2013 and 2012, respectively. These impairments relate to fields where an impairment was indicated based on estimated future net cash flows from the properties. Gains (losses) from derivative financial instruments. We utilized oil price swaps to manage our exposure to oil prices and protect returns on investment from our drilling activities in 2012 and 2013. Gains (losses) on derivative financial instruments were a loss of $8.4 million in 2013 and a gain of $21.3 million in 2012. Our total net cash received from derivative financial instruments was $2.3 million in 2013 and $9.8 million in 2012. The following table presents our crude oil equivalent prices before and after the effect of cash settlements of our derivative financial instruments: Interest expense. Interest expense increased $15.3 million (26%) to $73.2 million in 2013 from interest expense of $57.9 million in 2012. The increase was primarily related to a reduction in the interest we capitalized in 2013. We capitalized interest of $4.7 million and $20.9 million in 2013 and 2012, respectively, which reduced interest expense. We had interest expense allocated to discontinued operations of $8.4 million and $16.3 million in 2013 and 2012, respectively, of which $2.0 million and $9.6 million, respectively, was capitalized. Average borrowings under our bank credit facility decreased to $201.5 million in 2013 as compared to $482.7 million for 2012 and the average interest rate on the outstanding borrowings under our credit facility of 2.6% in 2013 was lower than the interest rate of 3.0% in 2012. Interest expense related to our outstanding senior notes increased by 11% due to the issuance of 9 $^{1}$⁄ 2% senior notes in June 2012 offset in part the redemption of 8 $^{3}$⁄ 8% senior notes in November 2013. Income taxes. The benefit from income taxes from continuing operations increased in 2013 to $56.2 million from $50.6 million in 2012 due to the higher net loss from continuing operations in 2013. Our effective tax rate of 34.5% in 2013 and 32.9% in 2012 differed from the federal income tax rate of 35% primarily due to the effect of nondeductible compensation and state income taxes. Net income. We reported a loss from continuing operations of $106.7 million or $2.22 per share for 2013 as compared to a loss of $103.1 million or $2.22 per share for 2012. The loss in 2013 included 49 Average Realized Oil Price: 2012 2013 Oil, per barrel ............................................ $101.09 $100.20 Cash settlements on derivative financial instruments, per barrel ..... 5.44 0.99 Price per barrel, including cash settlements on derivative financial instruments .................................. $106.53 $101.19