needed a help...

 needed a help in Oracle R12, i.e.
 
Case:
 
Item A, Price Rs.100,
Item B, Price Rs.150
 
But when i sell a combo pack of A & B , the Price becomes Rs.200 for both the items combined.
 
Can you guide me how do i map this in R12.
ail id : parambirb@evosys.co.on