I've got good news, and I've got bad news. The good news is that your cylinders in boxes - the harder part of the challenge - is well done. The bad news is that you appear not to have followed the instructions for the cylinders around arbitrary minor axes, and as a result, ended up making the same mistake throughout the whole set.

The issue is that the assignment section of the challenge states - in bold - that you should be varying the rate of foreshortening on your cylinders, as shown here. You did not. That's a problem, but what you actually did was eliminate the foreshortening from your cylinders by having the side edges run parallel on the page, effectively forcing the vanishing point governing them to infinity (in the manner discussed back in Lesson 1).

This unfortunately is incorrect. We do not control where the vanishing point goes - we control the way that set of edges (or in this case, the form) is oriented in 3D space, and it is that which determines the vanishing point. There is only a limited set of circumstances that puts a vanishing point at infinity - it occurs when the set of edges it governs in 3D space run perfectly perpendicularly to the viewer's angle of sight, basically going across their field of view without slanting towards or away from them through the depth of the scene. Given that this challenge has us rotating our forms freely and randomly in space (like in the 250 box challenge), we can pretty much presume that this perfect of an orientation would not occur, and that we should stick to working with convergences towards concrete vanishing points - even if that convergence is very slight and gradual. As long as it's noticeable, so that the viewer doesn't pick up on something being a little off when the edges tell us the cylinder is oriented in a specific fashion, but that is contradicted by other elements of the cylinder.

In essentially attempting to simplify the challenge beyond what is assigned, you ended up in a bit of a pickle, so unfortunately you will need to redo this section. When you do, be sure to draw through all of your ellipses two full times before lifting your pen, as is necessary for all the ellipses we freehand throughout this course.

Continuing onto your cylinders in boxes, your work here is much better. This exercise is really all about helping develop students' understanding of how to construct boxes which feature two opposite faces which are proportionally square, regardless of how the form is oriented in space. We do this not by memorizing every possible configuration, but rather by continuing to develop your subconscious understanding of space through repetition, and through analysis (by way of the line extensions).

Where the box challenge's line extensions helped to develop a stronger sense of how to achieve more consistent convergences in our lines, here we add three more lines for each ellipse: the minor axis, and the two contact point lines. In checking how far off these are from converging towards the box's own vanishing points, we can see how far off we were from having the ellipse represent a circle in 3D space, and in turn how far off we were from having the plane that encloses it from representing a square.

In applying the line extensions as instructed (and you actually seem to have added a few more in your earlier ones, where you connected the contact points at the different ends, which is fine because they make sense and do not detract from the main ones included in the instructions), you've done a good job of progressing in this regard. I can see that you've definitely shown growth in regards to your estimation of the boxes' proportions, helping you to identify one that is quite close to correct, regardless of how they're oriented in space. This should come in quite handy in the next lesson.

But, before you can get to that, I will require you to redo the 150 cylinders around arbitrary minor axes. Be sure to vary that foreshortening between dramatic and shallow (but not eliminating it entirely) this time.