This is a simple interest problem. We are going to use the formula:
[tex]I=Prt[/tex]
Where I is the interest she has to pay for her loan, P is the amount she financed, r is the interest rate (in decimal), and t is the number of years.
Replace the values to get:
[tex]I= (18489)(0.035)(4)[/tex]
[tex]I=2588.46[/tex]
Now that we have the interest she paid, we just need to add them to the value she paid to get the total cost she paid:
[tex]18489+2588.46=21077.46[/tex]
We can conclude that the total cost of the car that she financed will be $21,077.46
