What premise about share value underlies the constant-growth valuation (Gordon growth) model that is used to measure

Question:

What premise about share value underlies the constant-growth valuation (Gordon growth) model that is used to measure the cost of equity, rs?

Common Stock
Common stock is an equity component that represents the worth of stock owned by the shareholders of the company. The common stock represents the par value of the shares outstanding at a balance sheet date. Public companies can trade their stocks on...