I need to find the COGS and the BI. How do I calculate one without the other?

Beginning Inventory will be the Ending Inventory amount on your previous period balance sheet.

For example your beginning inventory amount for the year 2012 will be your inventory amount on your 2011 balance sheet.

In Some cases Beginning Inventory is $ 0
If its not given you can assume its $ 0
But do you have something there like Finished GOODS in place on Beginning Inventory
Or Ending Inventory from Last year will be beginning inventory of this year.

So here is how you do it

Beginning Inventory $ 0
+ Purchases
(LESS PURCHASES discounts, Returns and allowances)
= COGs PURCHASED + FREIGHT IN
Total cost of goods available for Sale
- Ending Inventory
= COGS SOLD