At what points is the marginal benifit of applying additional fertilizer no longer grater than the marginal cost of the fertilizer

After hearing a knock at your front door, you are surprised to see the prize patrol from a large, well-known magazine subscription company. it has arrived with the good news that you are the big winner, having won $21 million. you have three options.(a) receive $1.05 million per year for the next 20 years.(b) have $8.25 million today.(c) have $2.25 million today and receive $750,000 for each of the next 20 years. your financial adviser tells you that it is reasonable to expect to earn 13 percent on investments.