Zachary was naturally shrewd enough to read Jacob's intention.
In reality, he wasn't offering to pay just because he wanted the profit. He merely wanted to get in Jacob's good graces. After all, wouldn't Jacob be even more grateful that he wasn't just helping his revenge but also helping him make money?
As such, he didn't hesitate to tell Jacob, "Well, chief—since you'll be paying, I will make sure that you will get every cent of profit that you deserve."
Jacob was grinning ear-to-ear, but he