I just need help with the dollar weighted average please. thank you (:

A manager buys three shares of stock today, and then sells one of those shares each year for the next 3 years. His actions and the price history of the stock are summarized below. The stock pays no dividends. Time Price 0 $ 180 Action Buy 3 shares Sell 1 share 1 200 2 200 Sell 1 share Sell 1 share 3 200 Required: a. Calculate the time-weighted geometric average return on this portfolio. (Do not round intermediate calculations. Round your answer to 2 decimal places.) Geometric average return 3.57 % b. Calculate the time-weighted arithmetic average return on this portfolio. (Do not round intermediate calculations. Round your answer to 2 decimal places.) Arithmetic average return 3.70 % c. Calculate the dollar-weighted average return on this portfolio. (Do not round intermediate calculations. Round your answer to 2 decimal places.) Dollar-weighted average return %