Entropy is described by the Boltzmann equation s = k*ln(A), where s is the entropy, k is the Boltzmann constant, and A is the multiplicity of that system (how many ways the state of a system can be organized).
Since this system has only one possible arrangement, the entropy would be:
s = k*ln(A) = k*ln(1) = k*0 = 0.
The absolute entropy of this system would be zero.
Hope this helps!
