The Laiterie de Coaticook in the Eastern Townships of Quebec produce several types of cheddar cheese. It markets this cheese in four vareties: aged 2 months, 9 months, 15 months and 2 years. At the producer's store, it sells 2 pounds of each variety for the following prices: $7.95, $9.49, $10.95, and $11.95, 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 $7.95 immediately. If he ages the cheese, he must give up the $7.95 today to receive a higher amount in the future. What is the IRR (expressed in percent per month) of the investment of giving up $79.50 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?