Answer:
40,320
Step-by-step explanation:
He can pick any one of the eight for the first examination.
He can pick any one of the remaining 7 for the 2nd examination.
He can pick any one of the remaining 6 for the 3rd examination.
...
He can pick any one of the remaining 2 for the 7th examination.
There's one left for the 8th examination.
Thus, there are 8×7×6×5×4×3×2×1 = 8! = 40,320 different possible orders in which the tubes can be examined.
