To find the annual percentage rate (APR) earned by the investment, we need to solve for the interest rate, r, in the formula:
A = P * (1 + r/n)^(nt)Where:
A = $28,000
P = $20,000
t = 120 months
n = number of times the interest is compounded in one yearRearranging the formula to solve for r, we get:r = n * ((A/P)^(1/nt) - 1)We can estimate the value of n by assuming it is 12 (since the investment compounds monthly) and solving for r using a trial-and-error method.If we plug in n = 12 into the formula, we get:r = 12 * ((28,000/20,000)^(1/12*120) - 1)r = 0.0445 or 4.45%
So the APR earned by the investment is approximately 4.45%.