The regulations governing Take-off Alternates are laid down by the Joint Aviation Authorities, (JAR-OPS 1.2959(b) and 1.297(a)). The alternate must be located within 60 minutes at the one-engine inoperative cruising speed for a two engined aircraft, and 120 minutes at the one-engine inoperative cruising speed for a three or four engined aircraft. There are also some additional rules for ETOPS aircraft.
However, these are the maximum distances, and any company may write their own rules, so long as they are within these limits.
The alternate minima rules are for planning purposes only. Once a flight has commenced, then any airfield can be used as an alternate so long as it is above operational minima.
However, most of this is irrelevant to your question. What the interviewer is asking is 'Would you bust minimums and risk all of the passengers to save the life of one passenger who might die anyway?' Whatever you might do in practice then, at the interview, the answer has to be NO.
Airclues