Earths surface area is 5.1x10^8 km^2, and its mean thickness is 35 km with a mean density of 2.8 g/cm^3. The two most abundant elements in the crust are oxygen (4.55x10^5 g/1000 kg) and silicon (2.72x10^5 g/1000 kg). The two rarest elements are ruthenium and rhodium, each with an abundance of 1.0x10^4 g/1000 kg. What is the total mass of these four elements in the Earth's crust??
show work please!!!!!
show work please!!!!!