I think this is actually fair; even Strang, after all, provides answers to only select problem sets (e.g. only odd problem sets in Linear Algebra if I recall co

I think this is actually fair; even Strang, after all, provides answers to only select problem sets (e.g. only odd problem sets in Linear Algebra if I recall correctly) though to be fair to Strang, it seems to me that in his case, it's more a matter of "if you are unsure, come and ask me" and probably not the case of maximizing profits.