12. A device that has two components fails if at least one of its components breaks down.

The device is observed at a random time. Let Ai, 1 ≤ i ≤ 2, denote the outcome that the ith component is operative at the random time. In terms of Ai’s,

(a) define a sample space for the status of the system at the random time;

(b) describe the event that the device is not operative at that random time.