From these data, the values characterizing a time development
of cumulative costs for the subsystem repairs were calculated.
Table 1 provides a survey of the calculated values. The
method of least squares was applied to these discrete values to
develop a third-order polynomial approximation of the
cumulative repair costs of the subsystem (see Fig. 5). Then, by
suitable conversion of this polynomial function, a course of the average unit cost for repairs and the instantaneous unit cost
for repairs was obtained. A mileage of 1 kilometer was used as
a unit of service to which the unit costs are related. From the
subsystem acquisition price of $12 000, a time dependency of
the average unit cost for subsystem acquisition was also
derived.