A certain radio station plays songs from the 70's, 80's, and 90's. We know that 20% of the songs on the station are from the 70's; 37% are from the 80's; and 43% of the songs are from the 90's. Let be the number of songs you listen to until you hear the first one from the 90's.
a. What is the expected value of X?
b. What is the standard deviation of X?
c. Show the labeled graph of the mass for this story.
d. Show the labeled graph of the CDF for this story.