Need PL/SQL function to get actual unit cost of a cost accounting distribution

Summary

I need to call a PL/SQL function or write a query that will get me the actual combined layer cost of a single cost accounting distribution

Content

For the transaction below for a qty of 20 there is one associated transaction_id in cst_transactions, the unit cost of qty of 10 comes from layer 1 and the unit cost of the next 10 comes from layer 2. I'm writing a report that combines GL and cost accounting distribution information and I need the unit cost for the distribution. The link isn't working in the cost accounting area on this site so I posted this in the inventory area.