Suppose within every minute, the probability that there is fire in the room is p. If there is fire, the probability that the alarm sounds is q. If there is no fire, the probability that the alarm sound is r.

1. Give the probability that there is fire if the alarm sounds.
2. Give an example using concrete numbers of p,q,and r. If the experiment is repeated a million times, interpret the calculation in (1) in terms of frequencies.