Gina has borrowed 100 songs from her friend. she plans to download an equal number of songs on her music player each week for 5 weeks. the graph shows the number of songs left to download, y, for a certain number of weeks, x.

part a: what is the rate of change and initial value of the function represented by the graph, and what do they represent in this scenario? show your work to find the rate of change and initial value.
part b: write an equation in slope-intercept form to model the relationship between x and y.