%%% EX 6
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minor error:
goaltest should be placed inside the last if

%%% EX 7
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ok

%%% EX 8
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100	

%%% EX 9
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a)not a unifier!
b)ok
c)ok
d)ok

%%% EX 10
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you made it incredibly complex by not observing that
the problem depended on A,B,C only, due to the independent variable
roperty. 
However, ok.

"In math, there is no 5-second observation which cannot be
substituted by 30-minutes of nasty calculations." :-)