We have two urns. Urn 1 has 2 red balls and 3 yellow balls, while Urn 2 has 3 red balls and 7 yellow balls. We randomly select 75 balls form Urn 1, sampling with replacement. We independently randomly select 100 balls from Urn 2, sampling with replacement. Find the variance of the random variable defined as the number of red balls obtained from Urn 2 less the number of red balls obtained from Urn 1.