Hi Atul
You can assign a different valuation variant per Plant... In the screen of Valuation Variant, you will see a PUSH button called "Valuation Variant / Plant".. Click on that and you can maintain a diff val variant per plant
However, thats not the point here
You need to do Costing using ABC1 for Plant 1 first
Using the same ABC1, you can do for Plant 3.. Mixed costing will take place here... The QTy Structure type that you assigned in ABC3, you need to assign it in ABC1
Br. Ajay M