8. A and B start at the same time, their speeds are shown in the following graph. After 30 minutes, B has walked $\qquad$ meters more than A. 

保留源文本的换行和格式，直接输出翻译结果。
【Answer】 300
【Analysis】Distance covered by A in 30 minutes: $100 \times 10 + 80 \times 15 + 60 \times 5 = 2500$ meters Distance covered by B in 30 minutes: $100 \times 20 + 80 \times 10 = 2800$ meters
After 30 minutes, B has walked more than A by: $2800 - 2500 = 300$ meters