Projects NPV

A hazardous waste site will cost your company far into the future. One-time construction costs are $70 million in year 0 and $30 million in year 5. Containment tanks must be replaced every 20 years at a cost of $5 million. O&M costs are $1 million per year. The interest rate is I=10%. What single sum of money must be set aside in year 0 to cover all costs far into the future?