Start with
one quart = 32 oz
So
3 qt 8 oz = 3+8/32 qt = 3.25 qt
2 qt 9 oz = 2+9/32 qt = 2.28125 qt
Unit cost of Happy Juice = $7.28/3.25 qt = $2.24 per quart
Unit cost of Super Juice = $5.84/2.28125 qt = $2.56 per quart
Leave it to you to decide which juice is more expensive.