I also believe the answer is MNO, But I am unsure as my method seems to simple. PQRS LMNO QRS=MNO because they match up, which means if they are similar shapes the points should also match up when drawn. Because similar shape have congruent Angles then QRS must be equal to MNO
The volume of a rectangular prism is width×length×width. With the given volume of 24 you could find 2 ways with different sets of numbers that multiply into 24.