# Noise and vibration

It operates three machines, A, B, and C, in a large factory. Each sound power level is 100 dB, 95 dB, and 90 dB, and the number of equipment is 10, 20, and 15. At this time, the SPL of the factory was 65 dB. Determine the factory's sound pressure level(db) when A is reduced by 10 dB and B and C are reduced by 5 dB.

Please solve step by step with clear explanation.

Thanks in advance!