Official Solution: A juice bar mixed apple juice and berry concentrate to make 6 liters of a fruit drink. If apple juice cost $4 per liter, and berry concentrate cost $10 per liter, was the volume of apple juice used greater than the volume of berry concentrate used? Let \(x\) be the number of liters of berry concentrate used. Since the fruit drink was 6 liters total, the amount of apple juice used was \(6 - x\). The question asks:
Is \(6 - x > x\)?
Is \(x < 3\)?
So the question is equivalent to asking whether less than 3 liters of berry concentrate were used.
(1) Less than 4 liters of berry concentrate were used.
This tells us:
\(x < 4\)
This is not enough.
Not sufficient.
(2) The total cost of the apple juice and berry concentrate used to make the 6 liters of fruit drink was less than $39.
The apple juice cost $4 per liter, and the berry concentrate cost $10 per liter, so:
\(4(6 - x) + 10x < 39\)
\(24 - 4x + 10x < 39\)
\(x < 2.5\)
Since \(x < 2.5\), we know \(x < 3\). Therefore, more apple juice than berry concentrate was used.
Sufficient.
Answer: B