WDV of NCAs used as initial investment

Sir! In case of NPV , what if question provides following information instead of giving the "Initial investment amount" of the project :- To start this project co.s existing Non Current Assets were used at T0. The WDV of these assets was $4m and Market Value was $5m. In this question, to calculate NPV, which amount should I subtract ($4m or $5m) from "PV of Cash Inflows"??