Probability

#1
An MP3 player is loaded with 50 musical selections: 20 rock selections, 13 jazz selections, and 17 blues selections.?
Edit
The player is set on random play, so selections are played randomly and can be repeated . Determine the probability of each of the following outcomes.

(a) The first four selections are all jazz

(b) The first selection is a blues tune and the second is a rock tune.

(c) None of the first four selections is a rock tune.

(d) The first selection is rock, the second selection is jazz and the third selection is NOT blues.

(e) A selection is either a jazz tune or a blues tune.




In order to solve this problem, I tried totaling up all of the different types of music together & using that number that was given as the denominator but it was wrong. It has to be in decimal forum. For (a), I put 13/50 and it gave me 0.26 but that turned out to be wrong.