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The abacus might look normal to most, but Bai Ruozhu had keen eyesight and discovered that one of the beads had a tiny pointed spike protruding from it. The position of that bead was exactly where one would frequently fiddle with the abacus. Anyone who used the abacus was likely to prick their finger on that well-concealed spike.
Of course, a small prick wouldn't change much, but what was truly important was that this tiny spike had been coated with a bit of poison that caused dizziness.
If she had used the abacus and pricked her finger, then become dizzy from the poison, her calculation speed would inevitably be affected, and she might even make mistakes.
Li Dan had planned this out very carefully indeed!
Bai Ruozhu glanced at Li Dan, deliberately looked at the abacus, and then pushed it towards the table in front of her, clearly not intending to use it.
Li Dan's heart skipped a beat, had she seen through his scheme too?