On December 19, 2005, a group of private equity firms (Carlyle, CD&R, and Merrill) completed a buyout of Hertz, investing a total of $2.3 billion in equity. At that point, the PE sponsors owned 98.8% of the outstanding shares of Hertz (the PEs own 229.5 million shares). Subsequent events were as follows:

• On June 30, 2006, Hertz borrowed an additional $1 billion, used entirely to pay a $4.32 per-share special dividend to common shareholders.
• On Nov 15, 2006, Hertz completed an IPO at $15/share, with net proceeds of $1,425. The proceeds were used to repay the $1 billion loan, with the remainder used to pay a dividend to the pre-IPO shareholders. A total of 101.47 million shares were sold to new investors in the IPO; of those, 13.24 million were shares previously owned by the PE firms and the remainder were newly issued shares. Post-IPO, the shares were valued at $15/share.
• On June 12, 2007, The PE firms sold 51.75 million shares owned at $22.25 per share.
• On Dec 31, 2008, the PE firms sold the remaining shares they owned at $5.07.

Calculate the realized return (IRR) to the PE sponsors. You can use the excel function XIRR for your calculation.