replaces another mechanic of a lower skill level (as in the traditional BB system), then the
utilisation of the highest paid personnel may be maximised. On the other hand, by
replacing a mechanic of a higher skill level that is feasible, the probability of future
machine coverage (and hence, availability) may be increased. Since the machine coverage
of a mechanic from a higher mechanic category is typically greater, then when a later
machine breakdown occurs a greater probability may exist of having a mechanic that has
the skill level to immediately service it. As a result, the likelihood of maximising machine
availability while simultaneously maximising the utilisation of the high ranked mechanics
can be achieved.