I need to add all values from each week into one sum per month.

For instance, below is some of my data as it's set up for my pivot table.

A B C
1 Week DEPTID Week hrs
2 27-Dec 1000 8.00
3 3-Jan 8100 16.00
4 10-Jan 7000 1.60
5 17-Jan 7000 4.40
6 24-Jan 8100 20.00

On a separate (non pivot table) sheet, how do I show a sum by month, like
this:

A B
1 Dec Jan
2 8.00 42.00