**Solution:**

Total result = 0 sec to 40 sec

Total possible outcomes = 40

So, n(S) = 40

Favourable results = 0 sec to 15 sec

Favourable outcomes = 15

So, n(E) = 15

Hence, the probability that the music will stop in first 15 sec = n(E)/ n(S) = 15/40 = 3/8