Mr. Potter has just bought a house. He estimates that the roof will have to be renewed at a cost of $45,000 after 15 years. To cover these costs, he intends to save an equal amount of money at the end of each year, earning 6% annual interest rate. How much is such a yearly annuity? (18.33 marks) State and describe the underlying assumptions which you invoke in your calculation. (6 marks) Finally, describe how the concept of 'time value of money' informs the calculations you have performed to answer the question. (9 marks)