7. A water treatment plant has a remaining service life of 15 years. It costs $675,000 per year to operate and maintain the facility. The O&M costs are expected to stay constant for the first three years and then begin to increase by 0.5% a year for the next 12 years. What is the present worth of the facility if the nominal interest rate is 6%? (Hint: Draw the cash flow diagram for clarity)