Answer is A. Any help in how I get that answer would be awesome!

3. A piece of equipment was acquired on January 1, 2010, at a cost of S22,000, with an estimated residual value of $2,000 and an estimated useful life of four years. The company uses the double-declining-balance method. What is its book value at December 31, 2011? A) S5,500 B) S10,000 C) S11,000 D) S12,000