Depends on you are finance or Lease.
Finance: lets say 60 months.
20,000 ( car price ) +
3,000 ( 15% tax ) -
5,000 ( downpayment )
1,800 ( 20k + 3k - 5k * 10% rate )
-----------
19,800 total over 5 years.
/60 months.
-------------
~330/month.
Lease: lets say 48 months + 40% buy back
20,000 ( car price ) -
8,000 ( buy back )
-------------
12,000 ( car loan value ) -
5,000 ( downpayment )
700 ( 12k - 5k * 10% rate )
--------------
7,700 total over 4 years.
/48 months
--------------
~160/month +
24 ( 15% tax )
-------------
184/month
Clear?