How does circulation of old and new physical money work?

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everyday some coins and notes get old and need to be taken out of circulation (i imagine). how does a central bank (?) manage this flow of new and old cash? how do they know how much new cash is needed? how do they take some out and put new in? what do they do with old money that cant be used?

i was curious 🤷🏼‍♂️ happy for any and all feedback.

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