The glass window is installed in the window space and the intensity level of the sound entering via the window is decreased from 72 dB to 47 dB. The factor, by which the acoustic power entering the chamber is decreased by the glass window, is nearest to:
i) 2.2 x 10^-2
ii) 1.5 x 10^-1
iii) 1.0 x 10^-1
iv) 5.6 x 10^-2
v) 3.2 x 10^-3