If a1, a2, ..., a8 are eight numbers whose average is 40, and average of numbers at even places is 25, then average of numbers at odd places is :
1
220
2
320
3
55
4
100
If a1, a2, ..., a8 are eight numbers whose average is 40, and average of numbers at even places is 25, then average of numbers at odd places is :