Gave 1st one a quick read; quite confused:
Mr.X steps in Jan.1/86 and buys annuity (19 annual payments of $93,678.78)
at 9%, thus for $838,435.82.
So whatever happened before is now history; really, the whole problem could
start with the above; no need to bring in anything prior to Jan.1/86.
Then you've calculated that if Mr.X receives $596,411.93 on Apr.1/95 (so after
receiving 9 of the annual payments), then Mr.X has realised 10% on:
"THE ENTIRE TRANSACTION" : what d'heck does that mean?
Also confusing is your v = 1.08^(-1); how is it possible that the 8% (which was
the rate BEFORE Mr.X stepped in) be used in ANY calculation afterwards?
Can you clarify? If I'm dumb for having missed something: tell me