Multiple-liability imuunization

CFA Level III Fixed Income
#1

What does CFAI mean by:

’ liabilities should be discounted by the internal rate of retrun on the immunized portfolio" ???

Thanks

#2

to calculate pv(liab) you need a r (rate) to discount. this is the rate they are taalking about here.

and immunized portfolio you would have seen in the fixed income section - when they discuss the Immunization process.