X is not available.
Suppose Mr. A says, "X is not available."
Is it universally "X is useless"?
If so, then the perception that "X is not available" would be shared.
Unless you have a very limited opportunity to try out X to see if you can use it.
There are those who can use X and those who cannot, and Mr. A is the latter.
'Usable' is Attributes of relationships rather than single attributes.
Relationship between tools and users, challenges and solutions
Only "usable" when well matched.
Useless.
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