user
Calculate the enthalpy change of isomerization for the conversion of n-butane to isobutane if the heat of combustion of n-butane is -2657.5 kJ/mol and the heat of combustion of isobutane is -2878.8 kJ/mol.
assistant
<|begin_of_thought|>

Deep Thought is thinking for 7.5 million years.

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The answer is 42.

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