What is the final noise level inside the classroom if there is a working generator outside with sound power level of $95dB$ and the transmission loss of the walls and window are given to be $60dB$ and $20dB,$ respectively. Area of the window is given as $5m^2,$ average sound absorption coefficient of walls$/$window is $0\mathrm{.}2$ and average sound absorption coefficient of floor$/$ceiling is $0\mathrm{.}3.$