39. Find two coprime four-digit natural numbers $A$ and $B$ such that for any natural numbers $m$ and $n$, the numbers $A^{m}$ and $B^{n}$ differ by at least 4000.
88.39. For example, the numbers $A=4001$ and $B=8001$ are suitable. The difference of any two of their powers is divisible by 4000 and is not equal to zero.