inventory closing before inventory closing

hi,

Can anyone let me know the procedure on which item cost is defined at the time of issuance before inventory closing in Microsoft Dynamics AX 2009.

for example i have inventory item AA which i have purchased 5 quantity at 10$ and on another day in the same month i purchased 3 more quantity of the same item at 11$. what will be item issuance cost within same month and in the next month before inventory closing.

Please note that we are using weighted average method.

I will appreciate immediate reply.

Regards,

Ali