2.13. When one purchases, as an asset, shares in a company, one also expects some regular dividends as part of the financial benefit of holding the shares. Generalize the arguments of Section 2.3 to derive a modified Black–Scholes equation when the asset in the portfolio also returns dividends at a known rate δ. That is, for each share held in the portfolio, over a small time interval Δt the dividend contributes δΔt to increasing the value of the portfolio.