$的均值=10000*3/4=7500方差=10000*3/4*（1-3/4）=1625根据切比雪夫不等式P{0.74< $/10000 <0.76}=( P{|$/10000-0.75 |<0.01}>=1-(1625/10000^2)/0.01^2 =0.8375
