Renata wins a $20 gift card to an online music site. After Renata purchases 16 songs, the gift card has a remaining balance of $0. Which equation represents the relationship between y, the remaining balance on Renata’s gift card, and x, the number of songs purchased? 4x + 5y = –100 5x + 4y = 80 4x + 5y = 16 5x + 4y = 20