In a certain class, 20% of students have an average weight of 64 kg, 35% of students have an average weight of 72 kg, 30% of students have an average weight of 68 kg, and the remaining students have an average weight of 82 kg. What is the average weight of all students in the class?
1
70.5 kg
2
80 kg
3
70.7 kg
4
70.9 kg