⑴.P=(1/3)³[1+(2/3)C[1,3]+(2/3)²C[2,4]]=17/81
⑵. P3=(1/3)³+(2/3)³=1/3
P4=(1/3)³×[(2/3)×3]+(2/3)³×[(1/3)×3]=10/27
P5=8/27
E(X)=3.96
⑴.P=(1/3)³[1+(2/3)C[1,3]+(2/3)²C[2,4]]=17/81
⑵. P3=(1/3)³+(2/3)³=1/3
P4=(1/3)³×[(2/3)×3]+(2/3)³×[(1/3)×3]=10/27
P5=8/27
E(X)=3.96