<image>Daniela fills a $3 \times 3$ table using the digits 1 to 9 so that each field contains only one digit. She has already placed the digits 1, 2, 3 and 4 in the table as shown in the diagram. Two numbers count as "adjacent" if the fields which they fill have one common side. When she has finished filling the table she realised: the sum of the numbers adjacent to 5 is 9 . How big is the sum of the numbers adjacent to 6?