The Virgo cluster contains about 1300 galaxies and is at a distance of 16 Mpc. The galaxies have an RMS velocity about their center of mass of 600 km/s. How many galaxies do we need to observe in Virgo to reduce the error in Ho (hubble constant) due to peculiar velocities to 5%? Hint: look up how you calculate the error on a mean if you don't know.