Consider two sets A and B, each containing three numbers in A.P. Let the sum and the product of the elements of $A$ be 36 and p respectively and the sum and the product of the elements of B be 36 and $q$ respectively. Let $d$ and D be the common differences of APs in $A$ and $B$ respectively such that $D=d+3, d>0$. $\| \frac{p+q}{p-q}=\frac{19}{5}$, then $p-q$ is equal to