Answer:
1/3 cup of juice per cup of berries
Explanation:
The table shows that if we go from 0 to 4 cups (a "run" of 4 cups), the juice output is 1 1/3 (or 4/3) (a "rise" of 4/3 cups), and so the desired constant of proportionality is the unit rate
(4/3) cups
------------------------ = 1/3 cup of juice per cup of berries
4 cups berries