Which of the following is true?

Group of answer choices

a. even a slight increase in the default rate of a sinking fund has a dramatic impact on its balance

b. a large increase in the initial amount of over-collateralization has a minimal impact on the terminal fund balance

c. an increase in the yield on a sinking fund has a negative effect on the fund balance

d. the fund balance will rise with decreases in the PSA prepayment rate