two - finish the value scale - make sure you have used cross hatching - this is important.
three - when you have that and have numbered the values 10 - 0 (10 for black 0 for white) think about how you would use cross hatching and directional lines to create a surface that shows light and shadow.
New assignment - draw three dimensional bubbles - like the blobs you see in a lava lamp - or an apple - using a directional lines for shading - not smudging. You must use the entire value scale and imagine a consistent light source. Remember what is closest to you is also the lightest! This is a short assignment.