One purchase Organization going to Purchase

1. For a certain purchase organization

For purchasing

PRODUCT-1, Purchase Order calculation schema C1 consists of (MRP, DISCOUNT)

PRODUCT-2, Purchase Order calculation schema C2 consists of (MRP, DISCOUNT, and EXSISE DUTY)

PRODUCT-3, Purchase Order calculation schema C3 consists of (MRP, DISCOUNT, EXSISE DUTY, and VAT)

Please tell me whether is it possible for a certain purchase organization have three calculation schema

According to my knowledge for a certain vendor as an example, vendor schema is –V1

For a certain purchase organization as an example, purchase organization schema is –P1

So there will be one calculation schema based on V1 & P1

Then how three calculation schema is possible for a certain purchasing organization

If three calculation schema is not possible for a certain Purchase organization, then how this organization form the purchase order for the above three different material.