Step 1: Given the arithmetic mean of \( a, b, c, d \).
The arithmetic mean of \( a, b, c, d \) is given by:
\[
\frac{a + b + c + d}{4} = 14 \Rightarrow a + b + c + d = 56.
\]
Step 2: Work with the second condition.
We are asked for the arithmetic mean of the quantities \( a + b \), \( c + d \), and \( a - b + c - d \). We have:
\[
a + b + c + d = 56 \quad \text{and} \quad a - b + c - d = 48.
\]
Thus, the arithmetic mean is:
\[
\frac{56 + 48}{3} = 34.67.
\]
Step 3: Conclusion.
So, Quantity B is greater than Quantity A.