Highlight dates which are X working days late

Hi, I need a formula for format conditioning which will highlight the Appointment date cells (Column C): if it is Location South (Column A),if there are no appointment dates (Column C), and if the Contact date (Column B) is 7 WORKING days late. ALL 3 of these conditions must apply otherwise I want no highlighting.

LOCATION	CONTACT DATE	APPOINTMENT DATE
North	08/07/17
North	01/07/17	03/07/17
South	01/08/17
North	07/07/17	29/07/17
South	26/07/17
South	02/07/17	29/07/17
South	01/07/17