10.4.3.2 __Model B - Same As Model
A Except Mission Duration Time, t is Probabilistic__

The operational readiness model of Eq. (10.72) can be extended
to the case when mission duration time t is not the same for each mission but
is distributed with a density q(t). We then get

Since the integrals in Eq. (10.78) are fixed numbers, we may
write:

and using the symbol P for P(t_{m} <
t_{d}), i.e., P = P(tm <
td), Eq. (10.78) may be written in the form:

In this equation R is the probability that the system returns
without failures from the last mission; Q = 1 - R is the probability that one
or more failures developed in the last mission; and P is the probability that
the system will be repaired before the next call arrives if it developed
failures. The mission times are variable here with density q(t).