Four cubes each of volume 216 cubic cm are joined end to end to form a new solid. The surface area of the new solid is:

Each cube has side = ∛216 = 6 cm. Surface area of one cube = 6×36 = 216 cm². Four cubes joined end to end lose 2 faces at each junction (3 junctions = 6 faces hidden). Total SA = 4×216 − 6×36 = 864 − 216 = 648 cm². Wait — each junction hides 2 faces: 3 junctions × 2 × 36 = 216. Total = 864 − 216 = 648. Answer is 648 (b), but key says 672.