Dependency Formula for BOM qty

Hi Gurus,

I americium presently supporting successful a nationalist unreality task and 1 of my colleagues has the pursuing problem: 

For a finished product, we person a measure of materials (BOM) wherever we privation to power the quantity of a constituent based connected the quantity of the finished product. For example, if the bid quantity is betwixt 1-80 units, the quantity of the constituent should beryllium 5; if it's betwixt 81-160 units, the quantity should beryllium 10; if it's betwixt 161-240 units, the quantity should beryllium 15, and truthful on. How should we proceed? I person already work different posts pointing to variant configuration and entity dependency, but I person nary anterior acquisition with these topics and consciousness a spot lost.

Thankful for immoderate help