What can you say about the value of stock with constant dividend growth where the growth rate is larger than the discount rate?

In the dividend discount model, the stock price increases at the rate of dividend growth (g), and g=ROE*b. Why or why not is it always in the best interest of shareholders if a company decides to reinvest a larger portion of its net income (increasing b)? Assume constant and positive ROE.

What are similarities between buying stocks on margin and buying call options for that stock? (Name any two)

How can a business use future for risk management?

How can an investor use derivative for risk management?