Concept:
To determine individual values, we need sufficient independent equations involving all variables.
Step 1: Analyze Statement I alone.
Let Bob = \(x\), then Alice = \(x + 50\).
Infinite values possible.
Statement I alone is NOT sufficient.
Step 2: Analyze Statement II alone.
\[
{Alice} + {Bob} = 200
\]
Two variables, one equation → infinite solutions.
Statement II alone is NOT sufficient.
Step 3: Combine both statements.
Let Bob = \(x\), then Alice = \(x + 50\).
\[
x + (x + 50) = 200 \Rightarrow 2x + 50 = 200 \Rightarrow 2x = 150 \Rightarrow x = 75
\]
So,
\[
{Alice} = 75 + 50 = 125
\]
A unique value is obtained.
Hence, both statements together are sufficient, but neither alone is sufficient.