Query problem

I have 3 tables, I want to show current stock quantity for each item.

Table item
<item_id>            <item_name>            <cost>
<selling_price>
P001                   A4 Paper                   10                   12
P002                   Pen                            2
3
P003                   Eraser                        1                     2
P004                   Book                         20                   25

Table stock_out
<item_id>            <qty>            <date>
P001                    4                   11-NOV-00
P002                    2                   02-NOV-00

Table stock_in
<item_id>            <qty>            <date>
P001                    10                01-OCT-00
P002                    10                01-AUG-00
P003                    10                01-JUL-00
P004                    10                01-AUG-00


How can I show the following result?
<item_id>            <qty>
P001                    6
P002                    8
P003                    10
P004                    10


THANKS
James