8. A lake has a volume of 700000 ma. At time t=0, the company starts a water cleaning process so that only fresh clean water flows into the lake. After 5 years, it found that the pollution in the lake is 60% of the original amount of pollution. If fresh water flows into the lake at a rate of r cubic meters per year and lake water flows out at the same rate, what is the value of r correct to the nearest thousands? (1 mark) O 71000 89000 O 81000 O None of above or below