A man stands at the midpoint between two speakers that are broadcasting an amplified static hiss uniformly in all directions. The speakers are 27.0 m apart and the total power of the sound coming from each speaker is 0.421 W. Find the total sound intensity the man hears when (a) he is at his initial position halfway between the speakers, and (b) after he has walked 3.0 m directly towards one of the speakers.

if you already have the answer to (a), then just work out how many periods there are in 1 minute, and that's the answer to (c).

it is given that trillions of microbes make up to 1% to 3% of the body mass.

let's take average of this percentage: 2%

consider the average mass of the human body as 70 kg.

then, trillions of microbes would have mass  

therefore, 100 trillion micro-organisms would weigh:

this is an approximate value and could change depending on the mass of the human body and percentage of the microbes present in it.

average mass per microorganism =