solver constraint
 

I used Solver to maximize the sum of a series of changable numbers. The
constraints are also given. However, the solver returns some solution that
doesn't meet the constraints. Why is that?
Another question, in solver constraint, there are =, <=, = etc. When I want
to use 0, shall I just choose = and set the value to a number that is very
close to 0, say 0.0000001?
Thanks a million!!!