Problem Set 7:

1a-c. Suppose we have a new type of MBS to accommodate the short-term investor. This new MBS security instrument contains only 5-year mortgages (in reality are rare if non-existent). ACME, a private secondary mortgage market, has pooled together ten $100,000 5-year mortgage loans. Note: To save space in writing out your work, you can scale the ten $100,000 to $100.

Calculate the duration for this MBS pool assuming annual compounding for three years at 10 percent interest which

a. is a zero coupon.

b. is an interest-only MBS.

c. is fully amortizable over the five years.

2. Now assume that the interest-only MBS in problem 2b. is prepayable (but not defaultable). Use the option-theoretic model to price this MBS. Interest rates have a 50% chance of going up 1% each year and a 50% chance of going down 1% each year. From your results, qualitatively compare the MBS value without prepayment to the MBS value with prepayment. Note: To save space in writing out your work, you can scale the ten $100,000 to $100. in your solution show the work/setup which includes the calculations for all steps in Slide 17s Option Pricing Lecture