Insert
at
end
of
20%
discussion:

A
final
factor
that
we
believe
supports
our
selection
of
a
20
percent
threshold
is
the
cost
of
installing
state­
of­
the­
art
controls
on
existing
units.
There
is
obviously
no
single
answer
to
the
question
of
at
what
point
that
cost
becomes
the
deciding
factor
in
an
owner's
decision
whether
to
replace
a
piece
of
equipment
and
incur
that
cost,
since
much
will
depend
on
the
rate
of
return
on
the
investment.
Nevertheless,
we
think
it
is
reasonable
to
assume
that
if
the
cost
of
the
controls
is
greater
than
the
cost
of
the
replaced
equipment,
it
is
likely
to
operate
as
a
substantial
deterrent
to
replacing
the
equipment
at
issue.

That
is
likely
to
be
the
case
with
respect
to
electric
utilities
if
we
set
the
threshold
below
20
percent,
which
represents
the
approximate
cost
of
retrofitting
existing
plants
with
state­

ofthe
art
controls.
The
equation
is
similar
for
industrial
boilers.
Those
sectors
also
represent
a
substantial
segment
of
the
______.
While
the
costs
vary
widely
in
other
industries,

____.
