It took  a while for me to finish this work, and it looks not bad though. To finish this work, there are many steps, which i wasn’t so clear before. First i drawn the image of boxes from my angle, and using tracing paper to traced each part, and find its value in the value scale,  cut and paste. What i found out would be a challenge was that you have to figure out the value for each part of box. And it might feel like sometimes  they really look the same but actually they don’t. I saw the effect when i really done with the whole piece.