[libreoffice-users] Calc sliding scale formulae?

Hi,

I am using Calc 3.4.5 on openSuSe Linux 11.2

I am working on a spreadsheet to cater for the monthly measurement of 
household electricity consumption, new unit purchase and costing of used 
units.

The electricity supplier gives me the first 150 units of electricity at 
R1.29 per unit. The next 350 units are costed at R1.35 per unit. 
Thereafter the units cost me R1.60 per unit. The monetary values per set 
amount of unit changes when the electricity provider increases prices 
i.e. the first 150 units might increase to R1.50 per purchased unit, the 
next 350 units might be costed at R1.55 and thereafter units will cost 
R2.00.

Each time I purchase electricity the units I am allocated are based on 
the above sliding scale starting from 0.

How can I work out the number of units I will receive for a given 
currency value i.e. R2000.00? i.e. x @ R1.29, y @ R1.35 and z @ R1.60= R2000

In addition how could I work out the value of units consumed using the 
above scale?

I am assuming the R values in the scale will change over time and these 
can each be averaged to calculate the cost of units used, but the 
problem is still to work out the formula.

Anybody have an idea if this is possible and where to start?

I am investigating results found on Google but would appreciate a 
pointer or three.

Thanks
Hylton
--
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Hylton is a Lions Club member of Lions Club of Fish Hoek (District 410A)
http://e-clubhouse.org/sites/fishhoek/index.php being part of the worlds
largest non profit NGO
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