通过初试的概率(2/3)*(3/4)*(1/2)=1/4.
B1,B2,B3全通过的概率(1/2)*(1/3)*(1/4)=1/24,
B1,B2通过,B3未通过的概率(1/2)*(1/3)*(1-1/4)=3/24,
B1,B3通过,B2未通过的概率(1/2)*(1-1/3)*(1/4)=2/24,
B2,B3通过,B1未通过的概率(1-1/2)*(1/3)*(1/4)=1/24.
被录取的概率(1/4)*(1/24+3/24+2/24+1/24)=7/96.
通过初试的概率(2/3)*(3/4)*(1/2)=1/4.
B1,B2,B3全通过的概率(1/2)*(1/3)*(1/4)=1/24,
B1,B2通过,B3未通过的概率(1/2)*(1/3)*(1-1/4)=3/24,
B1,B3通过,B2未通过的概率(1/2)*(1-1/3)*(1/4)=2/24,
B2,B3通过,B1未通过的概率(1-1/2)*(1/3)*(1/4)=1/24.
被录取的概率(1/4)*(1/24+3/24+2/24+1/24)=7/96.