The correct answer is that the interest earned in 6 months for an investment of $ 4,000.00 at an interest rate of 4.25% per year was $ 85. 
I = P * i * n where: I = earned interest, P = capital 
i = annual interest, n = time 
I =? P = $ 4,000.00 i = 4.25% n = 1/2 years 
I = $ 4,000.00 * 0.0425 * 0.5 
I = $ 85.00