Calculate 9 to 5 hrs

Calculate 9 to 5 hrs

I want to calculate number of business hours during 2 days. Please help.
For eg.
A
15/05/2013 13:25
19/05/2013 09:12
B
31/05/2013 10:20
22/05/2013 21:10
I want to get result in C column with possible following term..
6d 15h 20m or anything similar to above. Please help.