The Laiterie de Coaticook in the Eastern Townships of Quebec produces several types of cheddar cheese. It markets this cheese in four varieties: aged 2 months, 9 months, 15 months, and 2 jears. At the producer's store, 2kg of each variety sell for the following prices: $8.00,$10.00,$11.50, and $12.00, respectively. Consider the cheese maker's decision whether to continue to age a particular 2-kg 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 $8.00 immediately. If he ages the cheese, he nust give up the $8.00 today to receive a higher amount in the future. What is the IRR (expressed in percent per month) of the investment of giving up $80.00 today by choosing to store 20kg of cheese that is currently 2 months old and instead selling 10kg of his cheese when it has aged 9 months, 6kg when it has aged 15 months, and the remaining 4kg when it has aged 2 years? The IRR is % per month. (Enter your response as a percent rounded to two decimal places.)