CAT (QA) PYQs

Let A be the largest positive integer that divides all the numbers of the form $3^k + 4^k + 5^k$, and B be the largest positive integer that divides all the numbers of the form $4^k + 3(4^k) + 4^{k + 2}$, where k is any positive integer. Then (A + B) equals

For any natural numbers $m, n$, and $k$, such that $k$ divides both $m+2 n$ and $3 m$ $+4 n, k$ must be a common divisor of