1. **State the problem:** We want to find the balance of a savings plan after 18 months with monthly payments of 250 and a given APR (annual percentage rate). We also want to find the total invested and the total interest earned. 2. **Formula used:** The future value of an annuity formula is used for monthly payments with interest compounded monthly: $$A = P \times \frac{(1 + r)^n - 1}{r}$$ where: - $A$ is the balance after $n$ months, - $P$ is the monthly payment (250), - $r$ is the monthly interest rate (APR divided by 12), - $n$ is the number of months (18). 3. **Important rules:** - Convert APR to a decimal before dividing by 12. - Payments are made at the end of each month. 4. **Calculate monthly interest rate:** Assuming APR is given as a decimal $a$, then $$r = \frac{a}{12}$$ 5. **Calculate balance after 18 months:** $$A = 250 \times \frac{(1 + r)^{18} - 1}{r}$$ 6. **Calculate total invested:** $$\text{Total invested} = 250 \times 18 = 4500$$ 7. **Calculate total interest earned:** $$\text{Interest} = A - 4500$$ Since APR is not specified, the exact numeric answer cannot be computed. Replace $a$ with the APR decimal to find the final values.