Line L1 is parallel to the plane P.
L2 is parallel to L1 and lying in the plane P.
Now, normal of the plane containing L1 and L2 both is ⊥ to the plane P and the lines.
∴ Direction ratios of normal
=∣∣
∣
∣∣^i^j^k31−3435∣∣
∣
∣∣
=14^i−27^j+5^k
Hence, equation of the required plane is
14(x−1)−27(y−2)+5(z−3)=0
or, 14x−27y+5z+25=0
∴a+b+d=14−27+25=12