I GIVE A BRAINLIEST When a song is sold by an online music store, the store takes some of the money, and the singer gets the rest. The graph below shows how much money a pop singer makes given the total amount of money brought in by the one popular online music store from sales of the song.

a. Identify the constant of proportionality between dollars earned by the pop singer and dollars brought in by sales of the song.

b. Write an equation relating dollars earned by the pop singer, y, to dollars brought in by sales of the song, x.