please explain with detalis:

Sentry Manufacturing paid a dividend yesterday of$5 per share (DO = $4). The dividend is expected to grow at a constant rate of 8% per year. The price of Sentry Manufacturing's stock today is $29 per share. If Sentry Manufacturing decides to issue new common stock, flotation costs will equal $2.50 per share. Sentry Manufacturin's marginal tax rate is 35%. Based on the above information, the cost of retained earnings is