Three in a shuffle

In my MP3 player, I have 55 distinct songs, all grouped under 10 different albums, and the number of songs grouped under Album $k$ is also $k$ (so there is 1 song in Album 1, 2 songs in Album 2 and so on). I turn on shuffle mode and the MP3 player randomly picks and plays a song.

If the MP3 player randomly picks and plays the next 2 songs without replacement, the probability that all 3 songs are in the same album can be expressed as $\frac{a}{b}$ , where $a$ and $b$ are positive coprime integers. What is the value of $a+b$ ?