1. The problem is to calculate the simple interest earned on a principal amount of 4000 at an interest rate of 3.5% over 6 years. 2. The formula for simple interest is: $$I = P \times r \times t$$ where $I$ is the interest, $P$ is the principal, $r$ is the annual interest rate (in decimal), and $t$ is the time in years. 3. Convert the interest rate from percentage to decimal: $$r = \frac{3.5}{100} = 0.035$$ 4. Substitute the values into the formula: $$I = 4000 \times 0.035 \times 6$$ 5. Calculate the interest: $$I = 4000 \times 0.21 = 840$$ 6. Therefore, the simple interest earned over 6 years is 840.