Two crystalline forms of white phosphorus are known. Both forms contain P4 molecules, but the molecules are

Question:

Two crystalline forms of white phosphorus are known. Both forms contain P4 molecules, but the molecules are packed together in different ways. The a form is always obtained when the liquid freezes. However, below 276.9oC, the a form spontaneously converts to the b form:
P4(s,a) → P4(s,b)
a. Predict the signs of ΔH and ΔS for this process.
b. Predict which form of phosphorus has the more ordered crystalline structure (has the smaller positional probability).