The first eight paychecks totaled 54,400. The total paid after the ninth paycheck will be 61,200.
Since 61,200 is less than the OASDI limiit of 95,200 for 2007 (102,000 for 2008) the rate is still 6.2%.
OASDI is 6800 x .062 = 421.60
HI is 6800 x .0145 = 98.60
For other year's rates for OASDI and HI see http://www.ssa.gov/OACT/TR/TR04/VI_OASDHI_payroll.html
I hope this is the information that you need.