Let X denote the block rate of the host hotel for a particular conference, and let Y denote the lowest room rate available in the host hotel outside of the conference block. For a conference that requires a two-night hotel stay, which one of the following expressions represents the least amount of discount on the conference registration fee that, according to the article, would be sufficient to deter conference attendees from employing the ROB strategy in choosing accommodations? A. X+Y2X+Y2
B. X−Y2X−Y2
C. X−YX−Y
D. X+YX+Y
E. 2(X−Y)