İnterest question for my exam toorrow

[Mhmdozer]

Hi everyone. I have a one question about interest rates for my exam, if you help I'd be happy.

A man buys car on instalment basis such that he pays 50.000 on signing of the contract and remaining in 4 equal instalments of 20.000 the first is being paid at the end of first year and so on for each year if the rate of interest is %8 effective, find the cash price of the car?

 

[Wilmer]

A man buys car on instalment basis such that he pays 50.000 on signing of the contract and remaining in 4 equal instalments of 20.000 the first is being paid at the end of first year and so on for each year if the rate of interest is %8 effective, find the cash price of the car?

Formula (present value of annuity):
p = a[1 - 1/(1+i)^n]/i

a = amount of payment (20.000)
i = interest rate (.08)
n = number of payments (4)
p = present value (?)

That will result in p = 66.243,
so price of car = 66.243 + 50.000 = 116.243

Curious: what is value in dollars of 20.000 ?