Perpendicular Lines Intersection Foot

Let a line l pass through the origin and be perpendicular to the lines
11:

→

r

=

^

i

−11

^

j

−7

^

k

+λ

^

i

+2

^

j

+3

^

k

,λ∈ℝ and
12:

→

r

=−

^

i

+

^

k

+µ2

^

i

+2

^

j

+

^

k

,µ∈ℝ.
If P is the point of intersection of l and l1, and Q(α,β,γ) is the foot of perpendicular from P on l2, then 9(α+β+γ) is equal to ______.