Answer:
To calculate the monthly installment for Justin's car loan, we can use the formula for the present value of an annuity:
PV = (PMT / r) x [1 - 1 / (1 + r)^n]
where PV is the present value of the loan, PMT is the monthly payment, r is the interest rate per period (in this case, per month), and n is the number of periods (in this case, the number of months in 4 years, which is 48).
We know that PV is the amount of the car loan, which is N$18500. We also know that r is 6% per year, which is equivalent to 0.5% per month (since there are 12 months in a year). Finally, we know that n is 48.
Substituting these values into the formula, we get:
18500 = (PMT / 0.005) x [1 - 1 / (1 + 0.005)^48]
Simplifying this expression:
18500 = (PMT / 0.005) x 36.4358
PMT = 18500 / 36.4358 / 0.005
PMT ≈ N$402.87
Therefore, Justin's monthly installment for his car loan is approximately N$402.87.