Unforseen

Are you saying that the minimum that you could have got based on you results is 65% and the max 86%? In that case, all we can say is that the MPS must be less than 86%.

If you really want to do this, you need to go back to the thread where about 100 people posted their results and work out all their maximums. The lowest of those will be an upper bound on MPS.

Chances are though, all passers maximums will be above 70%, so you'll be no closer to knowing the true MPS.