Find an orthogonal matrix $P$ that diagonalizes $A$ as shown below. That is, $P^TAP = D$, where $D$ is a diagonal matrix.

The product of the three elements in the first row of $P$ is $b$. The product of the three elements in the main diagonal of $D$ is $d$. $c$ is the rounding (or nearest) integer of $|b \times d \times 6|$. What is the value of mod($c$,5), where mod(.) is the modulo operator?