The first question, there are two possibilities: a allows, b does not allow; A is not allowed, and B is allowed.

The probability is P 1=P (A) × (

1-P (b)

)+P (b) ×(

1-P (A)

)=0.35

The second question, two possibilities, A is right; A is wrong.

The probability is p2 = 0.83+c 3/kloc-0 /× (1-0.8 )× 0.82 = 0.896.

I promise. Yes! ! !

Note: C3 1 means one of three times.

C3 1× (1-0.8 )× 0.8 2 means that there is an error three times and the other two times are correct.