Please help me solve this situation or point me in the right direction. (please bear with my poor english)

There are n candidates to be placed in n job positions.

Each candidate selects 3 positions wich are ordered according to his/her preference.

* Candidate cannot change this order *

Each candidate is then interviewed in his/her 3 chosen positions.

Job interviewers order candidates.

Candidates will be placed in the jobs they rated most highly as long they are placed highly in employer preferences.

For example:

Candidate A chooses X, Y and Z in this order

Candidate B chooses X, Z and Y in this order

Candidate C chooses X, Z and Y in this order

X chooses A,B, C in this order

Y chooses A,B, C in this order

Z chooses A,B, C in this order

This results in

A goes to X

B goes to Z

etc

The problem:

Candidates real preferences are only visible after the interviews (and not before) and beeing unable to change the predefined order results in less optimal placements. for exemple, even If A hates the X position aftr the interview, his placement can't be changed.

I need to somehow prove that candidates ought to make their choices *after* the interviews. This is intuitive but how can it be argumented?

Thanks in advance

PC