Write an equation to determine the total amount, ( p ), paid on a car after ( n ) months at $420 per month, including a $4500 downpayment.
a) ( p = 420n + 4500 )
b) ( p = 420n - 4500 )
c) ( p = 420n + 4500n )
d) ( p = 420n - 4500n )