Conditional formatting with if statement

[K120]

I created added conditional formatting to the Response Due column, to help me keep track of when response was due.
I only want the conditional formatting to be applied if the cell next to it is blank.
for example, the last one on my attachment is due 3/26/14 but I have already submitted a response (see column K)
What can I add so that only those dates next to a blank in column K get the conditional formatting?

Sample.jpg

[simarui]

add another rule to your dataset using the following formula to determine the formatting:

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Then make sure that rule is ranked first and check the "stop if true" box to the right.

[K120]

That worked great, Thank you!