Assistance required asap plz... Indian company on ecc 6.0

Assistance required asap plz...

The client requirements is on SAP ECC 6.0 , CIN

They are planning for a scheme as mentioned below..

For every 3 materials and an additional payment of Rs 10/- , the end consumer would have an option to buy another item eg : mug.

These would be sold to customers under taxable invoice @ applicable vat /cst rates.

can any of you assist on pricing configuration plz.

Thanks..