Determine the total minutes of call spend every 30 minute interval

[fritzkie_alexander]

I have a report that needs to determine the total minutes of call spend every 30 minute interval. Lets say there was a call that started at 9:29 with a duration of 31:47 (31 minutes and 47 secs). How can I distribute the duration of calls spent between 9:00 to 9:30 , 9:30 to 10:00, 10:00 to 10:30 etc.

Example Data:

Table to calculate the total minutes of call spend per 30 minute interval