Conditional Formatting With If Statement - Response Due Column

I created added conditional formatting to the Response Due column, to 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?

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