Chef and Subset Additions

Chef is asked to write a program that takes an array $A$ of length $N$ and two integers $X, Y$ as input and modifies it as follows: - Choose a random subset of elements of $A$ (possibly empty) - Increase all the elements of the chosen subset by $X$ - Increase the remaining elements in $A$ by $Y$ You are given $N$, $X$, $Y$, $A$ and the array $B$ that is returned by Chef's program. Determine whet