UPSC CDS Math Volume and Surface Area Questions

We have,
Six cubes with same edge 12cm are joint end to end.
Then total length of big cuboid (L)=12×6=72cm
and breadth ‌(B) and height ‌(H) is same 12cm.
so, total surface area of cuboid =2(LB+BH+LH)
=2(72×12+12×12+72×12)
=3744cm2