LaShawn wants to buy some music online. There are two plans to choose from. The first plan is a flat rate of $1.29 per download. The second plan has a membership fee of $21 and a fee of $.99 per download. Let x be the number of downloads and C be the cost. Plan 1:
C=1.29xC=1.29x
Plan 2:
C=21+0.99xC=21+0.99x
What is the constant rate of change for each relationship? And for Plan 1, how many downloads are possible if the total cost is at most $15?