Pooja got a new room heater for her bedroom. The temperature of the room rises by $2°\mathrm{C}$ if the heater runs for $3$ minutes. After every $3$ minutes, the heater stops for a minute and the temperature falls by $1°\mathrm{C}$. If the present room temperature is $12°\mathrm{C}$, find out after how much time the temperature becomes $38°\mathrm{C}$.