23. There are 3 separate datasets A, B and C. N refers to the size of each dataset and Xi refers to the individual data points in the datasets. Dataset A: N1 = 9, mean = 62, sd = 6. Dataset B: N2 = 5, sum of xi's = 104.5, variance = 18. Dataset C: N3 = 6, mean = 24, sum of xi's squared = 3690. The three sets are then mixed together. Find the mean and standard deviation for the 20 numbers combined. You can treat each dataset as a population, not a sample (the combined dataset is also a population)