Option one:
6000 x 0.15 ==$900 - this is the down payment.
6000 - 900 ==$5,100 - this is the balance left
5,100 x 0.15 ==$765 - this is simple interest on 5,100 for 12 months or 1 full year.
765/12 x 13 ==$828.75 - this is simple interest on 5,100 for 13 months.
$900 (down payment) + $5,100 (principal balance owing) + $828.75 (interest for 13 months)==$6,828.75 - total cost of option one.
Option two:
6,000 x 0.05 ==$300 - this is the down payment
275 x 24 months - or 2 years ==$6,600 - total of 24 monthly payments.
$300 (down payment) + $6,600 (total of 24 payments) ==$6,900 - total cost of Option two.
$6,900 - $6,828.75 ==$71.25 - difference between the 2 Options.