Purchasing Example
------------------

Background:

There are three suppliers of a good, and they have quoted various prices for
various quantities of product. We want to buy at least total cost, yet not
buy too much from any one supplier. Each supplier offers decreasing prices
for increased lot size, and these are all-item prices.

For example :

Supplier Max %age   Price 0-100       Price 101-200   Price 200+
Bob            40     9.2    100        9    200        7   1000
		       ^      ^	
	            price    breakpoint

i.e. if you buy 150 items from Bob, the total cost is 9*150.



Note that it will be necessary to set ZTOLST to say 0.000001 as 
scaling moves the refrow entries closer together than the default 
value of ZTOLST.