Which is the best pricing model for risky securities and why?

Refer below link

 

http://www.frbatlanta.org/filelegacydocs/nandi.pdf

This would actually depend on the component of the security, whether it is coupon bearing, discounted or dividend bearing security.
One good model would be the discounted cash flow model of valuation whereby the security can be evaluated based on current and future expected cash flows.
The problem with this model is determining the cash flows with an accepted accuracy level.
The best way would be to use a variety of valuation models in order to be able to have comparative prices on the security.
A more specific response to this question would of course be pertinnent on further details of the security in question.
   

I am sorry , i do not have sufficient experience to this subject.

i guess i may put8:10 %  of cost value