Time Average

Hello,
I have attached a file with this question.
In this file Col A represents time. I am trying to take time average in the group of 4.
I mean B1 is the time average of A1:A4, B2 is avg of A5-A8, B3 is avg of A9:A12 and so on.

How can I do the same for whole range?

Please help.

Thanks.