Suppose that it is 10:14 Monday morning, and the price of Microsoft stock is $17.80 per share, the company is currently paying a dividend of $0.50 per share this year, and its dividend is expected to grow at a rate of 7% per year. At 10:15, Microsoft releases new sales information that indicates that sales of its latest version of Windows have been much higher than expected, and the firm expects higher sales to continue into the future. This news causes you and other investors to revise upward your forecast of the growth rate of Microsofts annual dividend from 7% to 8%. At this higher growth rate, the present value of Microsofts future dividends rises from $17.80 to $27.

This was copied from a textbook, I want to know how they got to $27.