Value of N

In the diagram, a positive integer is to be placed in each of the nine boxes so that the products of the numbers in each row, column, and diagonal are equal. Some of the entries are already filled in. The number of possible values for N is
\textbf{(A) }4 \qquad
\textbf{(B) }15 \qquad
\textbf{(C) }9 \qquad
\textbf{(D) }6 \qquad
\textbf{(E) }12 \qquad