Use of stevens law in product formation

I have to solve problem related fruit yogurt formation with no added sugar. Information about the product is in pictures.

Ingredients: pasteurized and homogenized whole milk, strawberry, sugar, carrageenan, yogurt cultures (S. thermophilus ve L. bulgaricus), citric acid and flavor
A) If use aspartame as a single sweetener, how much aspartame should it be used? What are some important points to consider when aspartame is used in this type of product?
B) How about if a blend of aspartame and saccharin is used? How much of each should be used?
I am not getting what is use of R here and how can i get S, please help me