rewriting work......... 700 words..........

Develop a 700-word report including the following calculations and using the information to determine whether the new billing system has reduced the mean bill payment time:

• Assuming the standard deviation of the      payment times for all payments is 4.2 days, construct a 95% confidence      interval estimate to determine whether the new billing system was      effective. State the interpretation of 95% confidence interval and state      whether or not the billing system was effective.
• Using the 95% confidence interval, can      we be 95% confident that µ ≤ 19.5 days?
• Using the 99% confidence interval, can      we be 99% confident that µ ≤ 19.5 days?
• If the population mean payment time is      19.5 days, what is the probability of observing a sample mean payment time      of 65 invoices less than or equal to 18.1077 days? 

Format your assignment consistent with APA format. 

Please plagiarism free, she is acting to show how we got to the numbers we got so show work. Must have excel worksheet also.