We have two populations: Pop1 and Pop2. On Pop1 we have a random variable Y1 with mean value 32 and standard deviation 4, while on Pop2 we have a random variable Y2 with mean value 35 with standard deviation 3. Suppose we obtain independent random samples from each of the two populations, and each sample has 36 elements. Find the expected value of the random variable which assigns the sample average of Y2 for the Pop2 sample minus the sample average of Y1 for the Pop1 sample.