The probability of breaking through the first level is p (greater than 1)=3/4.

The second floor * * * has basic events {ω =, 2, 3, 4, 5, 3, 4, 5, 6, 4, 5, 6, 7, 5, 6, 7, 5, 6, 7, 8}.

The failure probability of the second level is p (the value is less than or equal to 4)=6/ 16=3/8.

So the probability of only getting through the first level is P=3/4 × 3/8=9/32.