please help this probability and statistics questions with clear explanation, thank you

Question 2 (20 marks) David is responsible to deliver posted letters arrived in an office every morning. His supervisor, Peter, has recorded the time (in minutes) David spent on delivering the letters in a sample of 14 mornings. The following are the records in ordered array: 39 41 42 44 45 45 46 49 52 54 55 55 56 k (a) It is known that the mean delivery time of the letters is 49 minutes. Find the value of k. (b ) Find the sample standard deviation and the sample variance. (c) Comment on the skewness of the data. State your reason with calculation. (d) Find the range and interquartile range of the data. (e) It is now 1 1:15 am and David started his delivery 10:25 am this morning. David's supervisor wants him to handle an urgent enquiry now. Using the above data as reference, what is the probability that he has not yet finished delivering the letters? (f) Peter just found that there is an old report of David's work performance. There is a record indicating that David spent a total of 220 minutes in 1 week (with 5 working days) to handle his job of delivering letters in the morning. Combine all observations made by Peter and from the old report, find the average time David spends on delivering letters in a morning