If the temperature is increased the particles gain more kinetic energy or vibrate faster. This means that they move faster and take more space.
Atomic mass = number of protons + number of neutrons = 4+5 = 9 amu
The S.I. unit for the measure of the pressure is the Pascal (Pa). 1 Pascal corresponds to

We can convert the number given by the problem into Pascal:

And since

, we have
Answer: a.) Roughness of the surfaces in contact with each other .
Higher the roughness of surfaces in contact with each other, greater is the friction between bodies. Force of friction will be less between smooth surfaces.
b.) Weight of the sliding/rolling body: greater the weight of the moving body on the surface, more is the force of friction on the body by the surface.
I hope this helps