total money spent only for months in 2014

[rybussell]

Test book attached...
I have four columns on the sheet..

Total Cost, Duration of months, Date Ended, Average monthly cost

Average monthly cost is total cost divided by duration of months... Easy..

What I need to do is total how much the cost would be only for months that have happened in 2014...

For most months, it would be as simple as month value of C column multiplied by average monthly cost. There are obviously some times where this wouldn't work, such as if the duration is shorter than the current total months of the year (IE it's July and the duration is only 3)...

I've done a few attempts with sumifs but this is beyond me at this point.

Any help would be greatly appreciated. I know this is a bit complicated and I'll be here to clarify any questions.

Thanks in advance!