You can retire a loan either by paying off the entire amount $8000 now, or by paying $6000 now, $2000 at the end of 5 years, and an additional $2000 at the end of 10 years. Find a cutoff value  such...

You can retire a loan either by paying off the entire amount $8000 now, or by paying $6000 now, $2000 at the end of 5 years, and an additional $2000 at the end of 10 years. Find a cutoff value
 such that if the nominal rate
 is
 then you should pay off the entire loan now, but if
, then it is preferable to wait. Assume that interest is compounded continuously.