A scatter diagram (XY) has points, which show the relationship between two sets of data. The relationship obtained is not clear; so you need to the line of best fit by having the line as close as possible to all the points. For accuracy purposes, you can calculate the line using the Least Square Regression.
case 1:
a) The distribution of sale price as well as delivery time is approximately normally distributed as observed from histogram and table of descriptive statistics. The average is considered as the best measure of central tendency in the case when distribution is normal. The average sale price is $356.74 per ton with a standard deviation of 38.59. The average delivery time is 0.373 minutes/ton.km with a low standard deviation of 0.169.
There are 15 customers with satisfaction level of 5. This is followed by 8 and 7 customers with satisfaction level of 4 and 6 respectively.