Expected Difference

Alice initially had $X$ stones. She divides the $X$ stones into $N$ piles where the $i^{th}$ pile contains $A_i$ stones. Now, she randomly selects a subset of piles $S$ such that every subset has an **equal** probability of getting selected. After selecting the subset, for every $1 \le i \le N$, - If $i \in S$, Alice colours all the stones in the $i^{th}$ pile `RED`. - If $i \notin S$, Alice co