<svg xmlns="http://www.w3.org/2000/svg" xmlns:wrs="http://www.wiris.com/xml/mathml-extension" height="44" width="33" wrs:baseline="29"><!--MathML: <math xmlns="http://www.w3.org/1998/Math/MathML" class="wrs_chemistry"><mfrac><msup><mi>&#x3C0;r</mi><mn>3</mn></msup><mn>3</mn></mfrac></math>--><defs><style type="text/css">@font-face{font-family:'math1437d7d1d97917cd627a34a6a0f';src:url(data:font/truetype;charset=utf-8;base64,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)format('truetype');font-weight:normal;font-style:normal;}</style></defs><line stroke="#000000" stroke-linecap="square" stroke-width="1" x1="2.5" x2="29.5" y1="23.5" y2="23.5"/><text font-family="math1437d7d1d97917cd627a34a6a0f" font-size="16" text-anchor="middle" x="10.5" y="18">&#x3C0;</text><text font-family="Arial" font-size="16" text-anchor="middle" x="18.5" y="18">r</text><text font-family="Arial" font-size="12" text-anchor="middle" x="24.5" y="11">3</text><text font-family="Arial" font-size="16" text-anchor="middle" x="16.5" y="40">3</text></svg>