A children's balloon weighing M=6,8M=6,8M = 6,8 g is filled with helium. What should the radius of the resulting ball be equal so that it is under normal conditions in a suspended state (does not tend up and not fall down)? The ball has the shape of a sphere, the pressure inside and outside the ball are equal. MHe=4MHe=4M_{He} = 4 g/mol, Mair=29Mair=29M_{air} = 29 g/mol. Give answer in cm.