Operating Costs  Marketing  General and administrative  Research and development  Operating Costs and Expenses by Business Segment  Domestic fixed communications 78 Our domestic fixed communications costs and expenses increased by 14.5% from NT$67.0 billion in 2010 to NT$76.7 billion  (US$2.5 billion) in 2011, primarily due to an increase of NT$9.7 billion (US$321.4 million) in interconnection and service expenses  mainly due to the change in policy for collecting the tariffs of fixed line-to-mobile phone calls. Since we are the market leader of the  local call services, in addition to the interconnection fees, we are required to pay transition fees to the mobile operators for a period of  six years. Our research and development expenses increased by 8.5% from NT$3.2 billion in 2010 to NT$3.5 billion (US$0.1 billion) in  2011. This increase was principally a result of an increase in research professionals and engineers.  Our general and administrative expenses increased by 4.2% from NT$4.0 billion in 2010 to NT$4.2 billion (US$0.1 billion)  in 2011. This increase was principally a result of new business in mobile industry in Mainland China and an increase in personnel  expenses mainly due to salary increases, additional employees and bonuses.  Our marketing expenses, which include personnel expenses, expenses relating to advertising and marketing-related activities  and provision for bad debt increased by 3.1% from NT$22.5 billion in 2010 to NT$23.2 billion (US$0.8 billion) in 2011. This  increase was principally a result of a NT$0.3 billion (US$11.5 million) increase in salary expenses due to headcount growth, and  NT$0.2 billion (US$7.0 million) in expenses relating to human resource outsourcing services for the sales division.  Our operating costs increased by 14.0% from NT$115.3 billion in 2010 to NT$131.5 billion (US$4.4 billion) in 2011. This  increase was principally a result of an increase of NT$8.1 billion (US$266.1 million) in cost of goods sold, an increase of NT$7.1  billion (US$232.9 million) in interconnection and service expenses mainly due to the change in policy for collecting the tariffs of  fixed line-to-mobile phone calls, an increase of NT$1.0 billion (US$34.5 million) in maintenance and material expenses due to  expansion of broadband facilities, a NT$1.0 billion (US$33.2 million) increase in corporate solution ICT costs due to the increase in  revenue, partially offset by a decrease of NT$1.8 billion (US$61.1 million) in depreciation.  Operating costs include depreciation and amortization expense, personnel expenses, cost of goods sold, interconnection and  service expense, costs of materials and maintenance and spectrum usage and license fees.  P AR T I Domestic Fixed  Communications Mobile  Communications Internet International  Fixed  Communications Others Adjustment Total For the year ended  December 31, 2011 Operating costs and  expenses 76.7 72.3 17.2 15.8 8.0 (27.6) 162.4 Depreciation and  amortization 20.1 8.3 2.3 1.3 0.3 － 32.3 For the year ended  December 31, 2010 Operating costs and  expenses 67.0 62.1 15.8 14.5 6.1 (20.5) 145.0 Depreciation and  amortization 21.9 8.2 2.2 1.4 0.3 — 34.0