If the average of 5 crates is 250, then their total = 5 × 250 = 1,250. To find the high end of the range for the fifth crate, make the other crates as light as possible: Make the two lightest crates 200 each, for a total of 400, and the two heaviest crates 300 each, for a total of 600; together, those four crates weigh 1,000 pounds, leaving 250 pounds for x. Because only (A) sets 250 pounds as the high end, you can eliminate (B), (C), (D), and (E).