Maths.

1.The loudness of sound is L(in dB) defined as
L=10 log I/Io, where I is intensity of the sound
(in W/m^2) and Io is the lowest intensity of a
sound that can just be heard.

a)Express log I in terms of L and log Io.

b)At the beginning of a football match, the noise
level was measured to be 70 dB.When team A
scored a goal, the sound intensity was increased
by 150%, find the loudness of sound level at that
moment in dB.
(6 marks)