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'Weights' printed from http://nrich.maths.org/
The largest total you can make is $20$ ($2A + 2C$).
The smallest total you can make is $-60$ ($2B + 2D$).
There are some totals that are easier to produce than others
(perhaps those that require just one or two weights), so it may be
a good idea to start with those and then build on them with a few