The Tillamook County Creamery Association manufactures Tillamook Cheddar Cheese. It sells the cheese in four​ varieties: aged 2​ months, 9​ months, 15​ months, and 2 years. At the shop in the​ dairy, it sells 2 pounds of each variety for the following​ prices: $ 7.00​, $ 9.50​, $ 10.95​, and $ 12.00​, respectively. Consider the cheese​ maker’s decision whether to continue to age a particular​ 2-pound block of cheese. At 2​ months, he can either sell the cheese immediately or let it age further. If he sells it​ now, he will receive $ 7.00 immediately. If he ages the​ cheese, he must give up the $ 7.00 today to receive a higher amount in the future. What is the IRR​ (expressed in percent per​ month) of the investment of giving up $ 70.00 today by choosing to store 20 pounds of cheese that is currently 2 months old and instead selling 10 pounds of this cheese when it has aged 9​ months, 6 pounds when it has aged 15​ months, and the remaining 4 pounds when it has aged 2​ years?

The IRR is _____​% per month. ​(Round to two decimal​ places.)