General and administrative  Research and development  Operating Costs and Expenses by Business Segment  Domestic fixed communications Mobile communications Internet  International fixed communications  Others  The costs and expenses from our other business increased by 31.7% from NT$4.6 billion in 2009 to NT$6.1 billion in 2010.  The increase was primarily due to the consolidation of our subsidiaries.  Our international fixed communications costs and expenses increased by 1.9% from NT$14.2 billion in 2009 to NT$14.5  billion in 2010. The increase was primarily due to an increase of NT$0.1 billion in equipment rental expense and an increase of  NT$0.1 billion in corporate solution services and ICT costs.  Our internet operating costs and expenses increased by 4.5% from NT$15.1 billion in 2009 to NT$15.8 billion in 2010. This  increase was primarily due to a NT$0.4 billion increase in leased line expenses.  Our mobile communications operating costs and expenses increased by 6.6% from NT$58.3 billion in 2009 to NT$62.1  billion in 2010. This increase was primarily due to an increase of NT$2.4 billion in cost of handsets sold, and an NT$1.0 billion  increase in leased line and internet access expenses.  Our domestic fixed communications costs and expenses decreased by 0.9% from NT$67.6 billion in 2009 to NT$67.0 billion  in 2010, primarily due to a NT$2.1 billion decrease in depreciation and amortization expenses reflecting a slowdown in capital  expenditures, partially offset by a NT$0.9 billion increase in corporate solution services and ICT costs and a NT$0.8 billion increase  in bonus.  Our general and administrative expenses increased by 6.6% from NT$3.8 billion in 2009 to NT$4.0 billion in 2010. This  increase was principally a result of a NT$0.1 billion increase due to the consolidation of our subsidiaries previously accounted for  under the equity method, and a NT$0.1 billion increase in bonus.  Our research and development expenses remained flat at NT$3.2 billion in 2009 and 2010.  Domestic Fixed  Communications Mobile  Communications Internet International  Fixed  Communications Others Adjustment Total 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 For the year ended  December 31, 2009 Operating costs and  expenses  67.6 58.3 15.1 14.2 4.6 (17.8) 142.0 Depreciation and  amortization  24.0 8.4 2.3 1.4 0.2 — 36.3 83 P AR T I