I need to conbime two items into one and later to shrink it again into two items and also to price i

have item A and item B1- I need to sell item A with Price 100 on a slaes order

2 - Also I need to sell item B with price 150 on a sales order

3 - also I need to combine the two items (item A and item  in one item C , I need to price item C and place it on a sales order

4 - Also I need item C to shrink it into item A and item B

 

How can I dod that?

 

thanks

Alex