An analyst does research about free cash flow and gathers the following information about a company:
·Cash provided by operating activities is $22000
·Cash used for fixed capital expenditures is $6000
·Net debt repayment is $850
·Interest paid is $3000
·Income tax rate is 35%
·Depreciation and amortization is $1000
The free cash flow to the firm is closest to:（）

A. $16950

B. $17950

C. $18950

在乒乓球比赛中，以2米/秒的速度运动的小球在0.01秒时间内以18米/秒的速度被反向打回，在此过程中，小球的加速度大小是（）。