The document discusses weighted average cost of capital (WACC) under the book value method. It defines WACC as the calculation of a firm's overall cost of capital that weights the cost of each category of capital (equity, debt, etc.) according to its proportion of the total capital structure. The document provides an example of how to compute WACC by assigning costs and weights to different capital sources - equity, debentures, preference shares, and term loans - and calculating a weighted average. It concludes that WACC is used to determine if a project's profitability justifies its financing costs and helps companies make better capital budgeting decisions.