Answer
$$\approx 0.66897$$
Work Step by Step
There are $40$ circuits, which crash independently with probability $0.01 .$ For the result to work, all $40$ circuits have to mange properly. This directly gives:
$$
\mathbb{P}(\text { product works })=(1-0.01)^{40}=0.99^{40} \approx 0.66897
$$
