A man pushes a box against the Wall just hard enough to keep it from sliding down. He pushes on the bottom corner of the box opposite of the wall. His arms are angled up at 15° while he
applies a 90N force. The static friction coefficient between the box and the wall is .05. What is
the mass of the box?

c. newton's third law of motion

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 =