please help this probability and statistics questions with clear step and details, thanks

a. Draw a graph for the following sales data: Year Sales (Em) 1985 9 1986 12 1987 17 1988 10 1989 6 1990 13 1991 20 1992 18 1993 9 1994 16 1995 22 (3 marks) b. Plot the trend line on the same graph using 5-year moving average method.. (5 marks) c. Calculate the trend line using the least-squares method, giving the values of a and b to 3 significant figures. Give an interpretation of the value of b. (12 marks)