Explanation:

Given that, length (l) = 14 m, breadth (b) = 12 m and height (h) = 13 m
∴The length of the greatest rod that can be put in box = Length of the diagonal of a box
= √l² + b² + h²
= √(14)² + (12)² + (13)²
√509 = 22.56 m