In figure skating, when skaters decide to team up to skate in pairs, it is important to find a partner of compatible weight and height. You can model a skater's weight as a normal distribution. For men, the average weight of a skater is 77 kg with a standard deviation of 4.4 kg. For women, the average weight of a skater is 50 kg with a standard deviation of 2.4 kg. Let be the random variable representing the weight of a skater and the random variable representing the weight of a skater. Define by the sum of the weights of the two skaters in the pair. It does not seem credible that the weight of the skater and the skater who form a pair is independent. If the correlation between the variables and is 0.68, what is the standard deviation of ?

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