A student completed four assignments. On the first assignment, there were 10 questions, and the student answered correctly. On the second assignment, there were 20 questions, and the student answered correctly. On the third assignment, there were 30 questions, and the student answered correctly. On the fourth assignment, there were 40 questions, and the student answered correctly. What was the student's overall percentage correct for all four assignments?
78
79
80
81
82
