Fix bug 3209, correct error in randomization.
Fix bug 3210, change to $showpartialcorrectanswers = 0.
Fix bug 3211, change to $showPartialCorrectAnswers = 0.
Fix bug 3222, correct description of colors for tangent lines.
Fix bugs 3244, 45, 46, 47, change "lbf" to "ft*lb" in correct answer.
Fix bug 3259, clarify solution text.