At 20C, the diffusion coefficient of hemoglobin molecules in water is D = 6.9x10^-9 m^2s^-1.

a) Assuming that the molecule is spherical, calculate its radius. The viscosity coefficient of water is 1.002x10^-3 kg m^-1s^-1; kB = 1.38x10^-23 J K^-1.

b) Calculate the average square distance traveled by the molecules in one direction within 30 minutes.