Let a circle $C$ of radius 5 lie below the $x$-axis. The line $L _ { 1 } : 4 x + 3 y + 2 = 0$ passes through the centre $P$ of the circle $C$ and intersects the line $L _ { 2 } : 3 x - 4 y - 11 = 0$ at $Q$. The line $L _ { 2 }$ touches $C$ at the point $Q$. Then the distance of $P$ from the line $5 x - 12 y + 51 = 0$ is