The dolomite is a mixed carbonate of magnesium and calcium. Magnesium and calcium carbonates both decompose on the heating to form the carbon dioxide and metaloxides (CaO and MgO). If 4.84g of residue consisting of CaO and MgO remains when 9.66g of dolomite is heated until decomposition is complete, explain what percentage by mass of the original sample was MgCO3?