Parplan Opinion Polls Ltd conducted a nationwide survey into the attitudes of teenage girls. One of the questions asked was 'What is the ideal age for a girl to have her first baby?' In reply, the sample of 165 girls from the Northern zone gave a mean of 23.4 years and a standard deviation of 1.6 years. Subsequently, the overall sample of 384 girls (Northern plus Southern zones) gave a mean of 24.8 years and a standard deviation of 2.2 years. Assuming that no girl was consulted twice, calculate the mean and standard deviation for the 219 girls from the Southern zone. ​