I want explanation with R language code for the following questions(Z-test)

1. In a certain factory there are two independent processes manufacturing the same item. The average weight in a sample of 100 items produced from one process is found to be 50g with a standard deviation of 5g while the corresponding figures in a sample of 75 items from the other process are 52g and 6g respectively. Is the difference between two means significant?

2. A machine turns out 16 imperfect articles in a sample of 500. After overhauling it turns 3 imperfect articles in a batch of 100. Has the machine improved after overhauling?

3. The CEO of a large electric utility claims that 80 percent of his 1,000,000 customers are very satisfied with the service they receive. To test this claim, the local newspaper surveyed 100 customers, using simple random sampling. Among the sampled customers, 73 percent say they are very satisified. Based on these findings, can we reject the CEO's hypothesis that 80% of the customers are very satisfied? Use a 0.05 level of significance.

4. According the the U.S. Department of Education, full-time graduate students receive an average salary of $12,800. The dean of graduate studies at a large state university in PA claims that his graduate students earn more than this. He surveys 46 randomly selected students and finds their average salary is $13,445 with a standard deviation of $1800. With alpha = 0.05, is the dean's claim correct?

humble request to tutors please give the only correct answers don't give the wrong answer if you don't know the answer please ignore so someone can give me the correct answers.