Split revenue line with SLA and derive amount based on Item cost

Summary:

We have scenario wherein the revenue line is to be split and the total revenue amount is to be broken down based on Item cost and Mgmt Fees

For example:

For a Revenue of $100

A/R Trade A/c $100
To Fulfillment Revenue $80 (Item cost * Qty = $8 * 10)
To Mgmt Fees $20 (Fixed Fee * Qty = $2 * 10)

Any suggestions if this can be achieved via SLA at AR Invoice ? How to access Item Cost (Inventory item with actual cost method) when defining User-Defined Formula?

Or is there any other way to manage this scenario?

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