7-8: 5 SEE ANSWER

Answer: 0.79 seconds

First, you need to find the noise reduction caused by this change. Use the formula: NR = 10 log (A2/A1)

Plug the values into the formula: NR = 10 log (489/58)

Solve the equation: NR = 9.3 dB

Now, find the reverberation time using the formula: Rt = (0.161V) / (A + (air X V))

Plug the values into the formula: Rt = (0.161 X 2400) / (489 + (0 X 2400))

Solve the equation: Rt = 0.79 seconds