GI finished products as a promotion

Hi All,

We have finished products A,B &C, the UOM is CAR and each CAR contain 12 PC, 24 PC & 48 PC for A,B &C.

There's products collection issued from marketing department as a promotion, we have for example collectionX. one carton of material collectionX contains 4 PC from material A, 3 PC from material B and 5 PC from material C.

I make a transfer of one carton from each finished material A,B and C from finished product SLOC to promotion SLOC to assemble my collections carton.

my question is how to assemble one CAR of material clooectionX in promotion SLOC from material A, B and C.

when making GI for one CAR of material promotionX it should issue from material A,B and C quantity of 4 PC, 3 PC  and 5 PC

so please advice how to map this scenario in SAP.

Thanks and Regards.