Jamie purchased a DVD that was on sale for 15% off. The sales tax in her county is 5%. Let y represent the original price of the DVD. Write an expression that can be used to determine the final cost of the DVD.

1 y − 0.15y
2 0.05(0.85y)
3 y − 0.85y + 0.05y
4 1.05(0.85y)