Independent samples of math scores from students in the U.S. and Europe were collected from normal populations. A sample of 50 students from the U.S. had an average score of 570 while a sample of 50 European students had an average score of 540. The population standard deviations for the average scores of the US and European students are 102 and 115 respectively. What is the lower confidence limit of the 95% confidence interval for the difference between the population means?

• A.-24.82
• B.-12.61
• C.-29.21
• D.-18.24