Read the following directions carefully and answer the questions and mark as follows:
Two concentric circles $C1$ and $C2$ with radii $r1$ and $r2$. The circles are such that $C1$ fully encloses $C2$, then what is the radius of $C1$?
1. The difference of their circumference is $k$ cm.
2. The difference of their areas is m sq. cm.
- If any one of the statements alone is sufficient to answer the question.
- If both statements individually are sufficient to answer the question.
- If both statements together are required to answer the question.
- If both statements are not sufficient to answer the question.