Hello this is all about statistics. Please help me answer the problems since i find it bery difficult. Thank you

1. Company G that hasthousands of convenience stores all over the country claims that their employees has a mean salary of Php 17,800 with a standard deviation of Php 5.000. A researcher surveyed a random sample of 24 employees and found that their mean salary is Php Php 16,100. Do these employees have lower salaries than the rest? Test the claim at 5% level of significance. 2. A researcher randomly selected 21 new born infant in Barangay A and found out that their mean weight is 6.1 Ibs with standard deviation of 0.6 Ibs. They also selected 19 new born infants in another barangay and found that their mean weight is 6.9 [bs with a standard deviation of 0.2 Ity. At 1% level of significance. Test if there is a significant difference between the two sample means 3. A teacher gives a 15-item diagnostic exam at the start of the semester and gives the some test at the end of the semester to check the progress of her students, Given the list of the scores below, test if there is a significant difference between the means at the start and the end of the semester. Use 0.05 for alpha. START OF SEMESTER END OF SEMESTER 11 11 11 15 10 11 5 9 14 10 14 14