I am having problem trying to write the equation that will sum up the total of hours listed in Column F if Column C = "PSL" but only if Column D is blank.

This one works for just summing everything equal to "PSL" in Column C
=SUMIF(C2:C29,"PSL",F2:F29)

Now I need to make it only sum if Column D is blank. Any suggestions?

Thanks,
Karen