Earth's surface are is 5.10 X 10^8 km^2; its crust has a mean thickness of 35 km and a mean density of 2.8 g/cm^3. The most two most abundant elements in the crust are oxygen (4.55 X 10^5 g/t, where t stands for metric ton; 1 t=1000kg) and silicon (2.72 X 10^5 g/t), and the two rarest non radioactive elements are ruthenium and rhodium, each with an abundance of 1 X 10^-4 g/t. What is the total mass of each of these elements.