Gmat prep Maths-谢谢

On his way to work, Leo listens to one of three radio stations, A, B, or C. He first turns to A, if A is playing a song he likes, he listens to it; if not, he turns to B. If B is playing a song he likes, he listens to it, if not he turns to C. If C is playing a song he likes, he listens to it, if not, he turns off the radio. For each station the probability is 0.3 that at any given moment the station is playing a song he likes. On his way to work, what's the probability that Leo will hear a song he likes. ( answer: 0.657)

此题无思路，请各位帮助

看错题了，嘿嘿

最先听a频道，遇到喜欢的歌的可能性是0.3

如果a 频道的不喜欢，听b频道，可能性为0.7*0.3，因为a频道的不好听

类似听c频道是0.7*0.7*0.3

加起来就是答案了