ABC Investments has purchased a new computer system for $1.4 million and decided to depreciate it over a 4-year period on a sum-of-years’ digits (SYD) method. ABC estimates that the salvage value will be $ 200000 at the end of the four years. What will be the depreciation expense for the third year（）

A. $ 300000.

B. $ 240000.

C. $186000.

（11分）一个质量为m="0.20" kg的小球系于轻质弹簧的一端，且套在光竖直的圆环上，弹簧固定于环的最高点A，环的半径R="0.50" m,弹簧原长L₀ =" 0.50" m，劲度系数为4.8 N/m，如图所示，若小球从图示位置B点由静止开始滑到最低点C时，弹簧的弹性势能=0.60J；求：

（1）小球到C点时的速度v_C的大小。

（2）小球在C点时对环的作用力的大小与方向。（g="10" m/S²).