Ok so heres a npc that I made (I got the dummy model from free models and I added the clothes)
And here is the menu (I made this all by myself)
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EXCHANGE
For Fragments to Cash: 65% of fragments * 200
For Cash to Fragments: 65% of cash / 2500
The result will be rounded so that it can be a whole number
Edit 1: I will remake the UI tomorrow. Reason: No output.