Data Base Help!!! Can someone solve this question in a relational algebra query without using max function

Write relational algebra expressions for the following queries based on the tables below.

Product(SKU, Description, Price, Location)

Guests(CardNo, Name, Address)

Purchase(CardNo, SKU, StoreNum, When, Markdown)

Store(StoreNo, Address, Phone)

Inventory(SKU, StoreNum, Qty)

No use Max to get the greatest discount ..

7. The greatest discount on any product (renaming can be used to calculate a derived attribute, e.g., 100%Markdown/PriceDiscount(...))