A stock culture of plasmid-containing Streptococcus cremoris cells is maintained for a period of several days. After this time, the fraction of plasmid-carrying cells is found to be 0.66. The specific growth rate of plasmid-free cells at the storage temperature is 0.033 h^-1 ; the specific growth rate of plasmid-containing cells is 0.025 h^-1 . If all the cells initially contained plasmid and the frequency of plasmid loss per generation is 0.003, how many days was the culture stored? Answer with the nearest whole number of days