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\twelvepointsanserif
\def\tty{\tt\obeylines\parskip=0pt}


{\obeylines\parskip=0pt
Tom Jennings\hfill 2 Nov 90
Fido Software
552-8156
}

Here is how I am calculating our share of the PG\&E bill. Please don't hesitate
to call if you think it's wrong.

First we need the cost per KWH and gas Therm, which I calculate from the main
part of the bill, by simply dividing the {\tt Amount} by 
the {\tt KWH/Therm used} column.
Here's a sample from the September 1990 bill:

\vskip\parskip
{\tty
\halign {
#\ \hfil&		% TYPE OF SERVICE
\ #\ \hfil&		% (from)
\ #\ \hfil&		% (to)
\ #\ \hfil&		% (days)
\hfil#\ &		% (prior)
\hfil#\ &		% (present)
\ #\ &			% (difference)
\hfil#\ &		% (multiplier)
#\ &			% (therms/KWH)
\hfil#\cr		% (amount)

Type of&SERVICE PERIOD\span\omit& Billing& METER READINGS\span\omit& Reading\hfil& Multiplier&Gas-Therms\hfil\cr
Service&From&	To&		Days&	Prior&	Present&	Difference\hfil&	&	ELEC-KWH\hfil&	Amount\cr
GAS&	8/10&	9/10&		31&	5151&	5175&		\hfil 24&		1.011&	\hfil 24&	22.74\cr
ELEC&	8/10&	9/10&		31&	1931&	2433&		\hfil 502&		20&	\hfil 10040&	1228.61\cr
\cr}
}
\vskip\parskip

Which works out to:

$$
{\$1228.61\over 10400} = \$.122 per KWH
$$
\dots and \dots
$$
{\$22.74 \over 24} = \$.948 per Therm
$$

Next we have to determine the total KWHs/Therms we have used. Since we don't 
have our own meter, I am using the ``THIS YEAR/LAST YEAR'' 
numbers from the PG\&E bill to determine our utility usage -- with the 
assumption that all of 
the increase in usage this year from last is ours. (This assumes that SMP's 
utility usage has not gone up -- to determine this we could use 
the ``THIS YEAR/LAST YEAR'' numbers for the last few years to calculate SMP's
utility usage increases -- but that's another story!) Below is the {\tt Monthly 
Comparison} fragment from the bottom of the same PG\&E bill:

\vskip\parskip
{\tty
\halign {
#\quad\hfil&		% THIS YEAR/LAST YEAR
#\hfil&			% (days)
\hfil\ #\quad&		% (billed)
\hfil#\hfil&		% (therms per day)
\ #\hfil&		% (elec kwh days)
\hfill\ #&		% (billed)
\quad#\cr		% (kwh / day)

MONTHLY&	GAS THERMS& 	&THERMS& ELEC KWH&		&KWH\cr
COMPARISON&	DAYS&	BILLED&	PER DAY& DAYS&		BILLED&	PER DAY\cr
THIS YEAR&	31&	24&	.8&	31&		10040&	323.9\cr
LAST YEAR&	32&	11&	.3&	32&		9280&	290.0\cr
\cr
\cr
	&	&{\rm 13}&	&	&		{\rm 760}&\cr
\cr}
}
\vskip\parskip

The difference this year to last year in this example is 13 Therms and 760KWH, 
respectively. All that is left is to multiply total Therms/KWH used by the unit 
rate:

$$
760 KWH \times \$.122/KWH = \$92.72 
$$

$$
13 Therms \times \$.948/Therm \ \$12.32
$$

$$
\$92.72 + \$12.32 = \$105.04 Total Due
$$

\bye