Please help me solve these problems. Please show all of the steps to each solution. Thank you!

1. A sound from a speaker has a sound level of 54dB at a distance of 12m from the speaker. What is the sound level at 24m from the speaker assuming a spherical sound wave?

2. A person’s weight in water is 7.0% of her weight in air. What is the person’s percent body fat. The density of fat is 0.90g/cm3. The density of muscle is 1.06g/cm3, and the density of water is 1.00g/cm3.

3 .A 180 km/h hurricane wind blows over a house. If the flat roof of dimension 6.2m×12.4m is lifted off the house. Assume that the roof is not nailed down, what is the weight of the roof? Hint: The weight of the roof is equal to the force due to the pressure difference between the inside and outside of the house over the roof. The density of air is 1.29 kg/m3.

4. A bat flying toward a wall at 6.0m/s emits a sound at a frequency of 35kHz. What is the frequency of the echo (sound reflected by the wall back to the bat) that the bat hear?