One of the methods for obtaining very low temperatures is based on the use of the dependence of the thermodynamic quantities of certain substances (paramagnetic salts) on the magnetic field induction B. In not too strong fields, the free energy of the salt has the form F = F0 - (a/T)B2. Determine the amount of heat absorbed by salt during isothermal demagnetization from field B = B0 to field B = 0 at temperature T.

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