<p>The difference between&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML" class="wrs_chemistry"><mo>&#8710;</mo><mi mathvariant="normal">H</mi><mo>&#160;</mo><mi>and</mi><mo>&#160;</mo><mo>&#8710;</mo><mi mathvariant="normal">U</mi></math>&nbsp;when the combustion of heptane liquid is carried out at a temperature T is equal to:</p>