Companies A and B differ only in their capital structure. A is financed 30% debt and 70% equity; B is financed 10% debt and 90% equity. The debt of both companies is risk-free.

1. Rosencrantz owns 1% of the common stock of A. What other investment package would produce identical cash flows for Rosencrantz?

The solution says buy 1% of the stock of B and borrow 0.01*(Da-Db) = 0.01 *(0.3-0.1) = 0.002

Could someone please explain the intuition behind multipling by Da-Db

Many thanks!!