1. **Problem:** Liu deposited 3500 into a savings account 2 years ago with a simple interest rate of 4%. We need to find how much interest Liu earned. 2. **Formula for simple interest:** $$I = P \times r \times t$$ where $I$ is interest, $P$ is principal, $r$ is rate (as a decimal), and $t$ is time in years. 3. **Calculate interest for 2 years:** $$I = 3500 \times 0.04 \times 2$$ $$I = 3500 \times 0.08$$ $$I = 280$$ 4. **Answer:** Liu earned 280 in interest after 2 years. 5. **Next, find interest for 10 years:** $$I = 3500 \times 0.04 \times 10$$ $$I = 3500 \times 0.4$$ $$I = 1400$$ 6. **Total amount after 10 years:** $$A = P + I = 3500 + 1400 = 4900$$ 7. **Answer:** The account would earn 1400 in interest, making the total 4900 after 10 years. --- **Note:** The user also asked a second question about depositing 600 at 2.5% to earn at least 120 interest, but per instructions, only the first problem is solved here.