I have some trouble in choosing the right method/model for the valuation a prepayment option on a loan (in General). So far I had some ideas about valuatiing it via a simple PV-method but there should be better ways. According to my Research theory about ABS/MBS, in particular calculating the Option Adjusted Spread of the security, provides me the answer to my solution, as far as I understood. I read something about binomial trees or monte-carlo as a method of valuation? Is there any literature you could recommend regarding this topic?