My idea is that using Classification of prime ideals of $\mathbb{Z}[X]$
I considered $(x,p)$ where $p>6$ is prime in $\mathbb Z$
or type of $(x^n)$ or $(p)$, but above is not contained in the given ideal and these last two are not prime or again not contained in $(6,x)$
Maybe some hint, answer would be much appreciated.