Chapter: added an example of joint probability visualization that's used in the exercise but not yet introduced in the chapter. Adds a few clarification points.
Exercise: clarified instructions, deleted a commented-out exercise that was moved elsewhere, corrected an incorrect solution
Chapter: added an example of joint probability visualization that's used in the exercise but not yet introduced in the chapter. Adds a few clarification points.
Exercise: clarified instructions, deleted a commented-out exercise that was moved elsewhere, corrected an incorrect solution
Also standardized code style