Mental and non-mental objects can be separate by using a.
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magnet

Explanation:

you can use MAGNET to separate non metals and metallic objects because it attracts metals and nonmetals were left.

by using  production possibilities graph.  opportunity costs are key expenses in financial matters and are utilized as a part of registering money saving advantage investigation of a venture. such expenses, be that as it may, are not recorded in the record books but rather are perceived in basic leadership by processing the money costs and their subsequent benefit or misfortune.

it is a better alternative