Per a financial analysts projection, DPs stock will be worth $60 per share in three years. The company just paid a dividend of $1.50 per share and expects an annual increase of $0.50 in dividend per share during the next three years. If you require a return of 20% on investments of similar risk, what is the maximum amount that you would be willing to pay for DPs stock?

(My professor said the answer is $39.86, but I can't figure out how or why.)