I know. Sollozzo asks Vito if he's worried about security for his $2 million and that the Tattaglias will guarantee it. Since he didn't mention any % cost to the Corleones for that guarantee, Sonny would naturally be curious. But Sollozzo must have planned to kill Vito anyway, so Sonny's malaproprism would not have changed his course.

"Generosity. That was my first mistake."
"Experience must be our only guide; reason may mislead us."
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