Official Solution: The range of a set is the difference between the largest and smallest elements of a set.
\(range_t=t_{max}-t_{min}\);
\(range_s=s_{max}-s_{min}\);
Question: \(range_{t \text{ and } s} \gt (t_{max}-t_{min})+(s_{max}-s_{min})\)?
(1) The largest element of \(T\) is bigger than the largest element of \(S\). Given: \(t_{max} \gt s_{max}\), so the largest element of combined set is \(t_{max}\) but we still don't know which is the smallest element of combined set:
If it's \(t_{min}\) then the question becomes is \(t_{max}-t_{min} \gt t_{max}-t_{min}+s_{max}-s_{min}\).
Or: is \(0 \gt s_{max}-s_{min}\) and the answer would be NO; If it's \(s_{min}\) then the question becomes is \(t_{max}-s_{min} \gt t_{max}-t_{min}+s_{max}-s_{min}\). Or: is \(t_{min} \gt s_{max}\) and the answer would be sometimes NO and sometimes YES. Not sufficient.
(2) The smallest element of \(T\) is bigger than the largest element of \(S\). Given: \(t_{min} \gt s_{max}\), so the largest element of the combined set is \(t_{max}\) and the smallest element of the combined set is \(s_{min}\).
So the question becomes is \(t_{max}-s_{min} \gt t_{max}-t_{min}+s_{max}-s_{min}\). Or: is \(t_{min} \gt s_{max}\)? And that is given to be true, so the answer is YES. Sufficient.
Answer: B