According to a November 2019 report by CNN, the startup company Heliogen has devised a high-heat solar oven that can be used to create concrete and steel without the use of fossil fuels. Currently, the creation of these materials produces 7% of the world's carbon emissions from fossil fuels. If the world's total carbon emissions in 2018 was 37.1 billion tons, how much of that carbon came from the creation of these building materials? Give your answer in billions of tons. Round to two decimal places.