The critical density of the universe is 5.80×10^?27 kg/m^3

A) Assuming that the universe is all hydrogen, express the critical density in the number of H atoms per cubic meter.

B) If the density of the universe is equal to the critical density, how many atoms, on the average, would you expect to find in a room of dimensions 4.80m*9.00m*3.60 ?

C) Find the number of atoms in the room in part (B) under normal conditions on the earth.