A real estate company is studying and comparing the property values of two different cities, M and N. They notice city M quadruples every 36 months. At the start of the study, city N had 2 times as large a property value as city M. After twenty-seven years, the property value in both cities was the same. The real estate agent was curious how long it took city N to double. Find the answer using proper mathematical conventions. First state the exact answer in fraction form, then express in years and months, rounded to the nearest month.