Consider 100 30yr mortgage loans packaged into a pass-through MBS with a 5.5% coupon. Assume there are 4 groups of borrowers, each with 25 identical loans. See below for a description of the different loans:

Group # of Borrowers Loan Size Wac

1 25 200,000 6.27

2 25 275,000 6.05

3 25 350,000 6.15

4 25 475,000 6.31

a. What is the size of the MBS (total principal outstanding)?

b. What is the simple average loan size of the underlying pool?

c. What is the weighted average loan size of the underlying pool?

d. What is the weighted average gross coupon (note rate) of the underlying pool?