I do not know how to calculate the dollar-weighted average return. The answer is 3.93% but i do not know how to get it.

You invested 2 million in ABC fund at the start of 2008.By year end, you had earned a 12% return, and added 1 million in further investment.By the end of 2009, you had lost 5%, and taken out 500,000. By the end of 2010, you earned 3% and invested another 750,000, By the end of 2011, you earned 8.5% and removed your entire remaining balance. Assuming all returns occur at the end of the year, followed immediately by any further investments or removals, what is your dollar-weighted average return across the period?