Hello I hope you can help

I have a monthly roster that looks like this
A....B......C.........D.........E...........F..... .....G
1................................ Mon.....Tues....Wed......
2..start..finish...HRS...3 Apr.....4 Apr...5 Apr.....
3..7:00..15:00..7:30.............................. ..........
4..7:00..15:30..8:00...TRICIA...SUE....THERESE
5..7:00..15:30..8:00.............................. ...........
6..7:30..13:00..5:00...JEANNE..ANNA...FIONA
8..7:30..16:00..8:00.................CHRIS........ ......

I would like to total the hours for each day. Hours are in cell D3:D8. So
monday would equal 13, tues 21 etc.
Is there a formula that I can place in the cell which will add the days
hours together?

Your help is greatly appreciated