Question

Dust particles are trapped on a surface. There are two energy levels particles can be in: absorbed on a surface with zero energy, and wiggling with energy E=3/2kT. However, since the surface area is limited, not all particles can be in any state. There are 1000 particles and 1000 "holes" for them, 20 % of which are the wiggling ones. What is the ratio of expected energy of the dust particles and kT?

Details and assumptions
The probability that a particle has energy E is proportional to exp(−E/(kT)).
The particles are identical.