Decimal Point is hosting Summer-Fest a large outdoor concert to celebrate the start of summer. The headline act is a rising rock group from Australia. During sound checks, the band's sound crew is responsible for setting various acoustic and electronic instruments to ensure a rich and balanced sound. The difference in two sound levels, B_1 and B_2=10log(I_2/I_1), where (I_2/I_1) is the ratio of their intensities.

a) Biff's drum kit is miked to produce a sound level of 150 dB for the outdoor venue. The maximum output of Rocco's normal electric guitar amplifier is 120 dB. What is the ratio of the intensities of these instruments? Explain why Rocco's signal needs to be boosted by a concert amplifier.

My answer: (which is correct) 1000

b) After a few heavier songs, the band plans to slow things down a bit with a couple of power ballads. This means that Rocco will switch to his acoustic guitar, which is only one ten-thousandth as loud as normally amplified electric guitar. By what factor should the sound crew reduce Biff's drums to balance the with Rocco's acoustic guitar?

My attempt: ( which is not correct)

But that is not correct, so could someone help me please with part b.