The common stock for El Viss Company currently sells for $$20$ per share. The firm just paid a dividend of $$1\mathrm{.}50,$ and the dividend three years ago was $$1\mathrm{.}30.$ Dividends per share are anticipated to grow at the same rate in the future as they have over the past three years. Flotation costs for new shares will be $6\%$ of the selling price. Calculate the following:

a$.$ the cost of retained earnings

b$.$ the cost of external equity capital