Q79. Let d be the distance of the point of intersection of the lines $\frac { x + 6 } { 3 } = \frac { y } { 2 } = \frac { z + 1 } { 1 }$ and $\frac { x - 7 } { 4 } = \frac { y - 9 } { 3 } = \frac { z - 4 } { 2 }$ from the point $( 7,8,9 )$. Then $\mathrm { d } ^ { 2 } + 6$ is equal to :\\
(1) 69\\
(2) 78\\
(3) 72\\
(4) 75