A rectangular parallelepiped steel, the number of meters long is the smallest composite number, the cross-sectional area is 0.02 square meters, and the steel weighs 7.8 tons per cubic meter. How many tons does this piece of steel weigh?
一根长方体钢材，长的米数是最小的合数，横截面面积是0.02平方米，每立方米钢材重7.8吨．这根钢材重多少吨？
<gadget id="calculator">4 * 0.02 * 7.8</gadget>
<output>0.624</output>

<result>0.624</result>