Grains of fine California beach sand are approximately spheres with an average radius of 50m and are

Grains of fine California beach sand are approximately spheres with an average radius of 50μm and are made of silicon dioxide, which has a density of 2600 kg/m3. What mass of sand grains would have a total surface area (the total area of all the individual spheres) equal to the surface area of a cube 1.00 m on an edge?